You are correct but it goes deeper than that for those of us who have been on the Usenet and on car forums for as long as both have existed (Usenet being longer of course).
There are mainly two BMW forums, where I think bimmerfest is the better one, but that's up to the beholder to determine.
Heh heh ... that was me (if you're talking E39 and not X5).
I already created a spreadsheet on that E39 forum of what I could figure out on my own for the various hose sizes. I was asking for further help, but nobody knows it (I'm AW on that forum).
What I find strange is... Nobody has ever measured the ID/OD/Length of the vacuum hoses in the E39?
On the Toyota forums, I found that same problem for the crush washers. Nobody on the forum thought to measure the crush washer OD/ID/Thickness?
Can you believe that? I must be odd - because I'm all for second sourcing, especially when you can often get better material (e.g., silicone, copper, whatever) at lower cost.
But you need the sizes.
For each bimmer model, there are about a score of common problems.
For the E39, offhand, they're . seat twist . abs trifecta . fsu/fsr fries . vapor barrier leaks . disa valve pin disintegration . cooling system leaks (mostly the behr expansion tank) . trunk loom fraying . headlight adjuster breaking (after 2001) . power steering bracket cracking (V8 only) . power steering hose leaking (I6 only) . CCV and dipstick tube clogging . VANOS o-rings disintegrating . rear tire negative camber inner wear (by design) . jack pads falling off (before the re-design) . dorman front window regulator plastic rollers . dorman rear window regulator lead crimp . windshield wiper pumps leaking . mechanical tensioners noisy (early models) . cluster pixels fail one by one (replaced under extra warranty) . mid pixels fail one by one (not covered after warranty expired) etc.
How's my list of *common* problems that almost every E39 (and E46 and E38) is affected by?
I know the window regulators better than anyone and I've been on the BMW forums for something like 20 years (or so) so I know exactly what you're saying.
There are always two types of people.
There is the type who bought the car for the image. And there is the type who bought the car because they thought it was good.
It's actually good - once you (repeatedly) fix the 20 things that go wrong on almost all of them. Some (like the DISA) you can use Gary's solution to redesign them, while others (like the CVV) you can use BMW's redesign, but others (like the cooling system if you don't go Zionsville) you just have to constantly replace.
You do learn EXACTLY why they fail though, and they often fail for the most ridiculous of reasons.
For example, the door window regulator you're talking about is Dorman where the Uro has (only recently) redesigned the rollers so that the wire won't fall off. That only works for the front. On the rear, the lead crimp falls off the wires. On both, the motor can fail but usually doesn't. Also the trolly bolts loosen up rather often, but mostly because people who replace the regulators don't locktite them. And lots of people who replace the regulators in the front forget to disconnect the battery before disconnecting the yellow airbag so they complain incessantly about the airbag light after a door regulator repair.
In the case of seat twist, it's the cable ends that get soft. In the case of the Bosch ABS trifecta, it's a wire that falls off its pin. In the case of the sitronic FSU, it's a MOSFET trace that cracks. In the case of the trunk loom, it's the wires that crack in the same spot. In the case of the Hella headlight adjusters, it's the brittle plastic. In the case of the DISA it's a plastic pin (which Gary replaced with metal) In the case of the VANOS (long story) it's said by Raj to be the buna In the case of the wiper pumps it's said to be the o-ring design In the case of the rear tires, just change 2 degrees to 0 degrees In the case of the behr cooling system - a key is never overfill it ever! In the case of the vapor barriers - bmw didn't apply enough adhesive In the case of the jack pads - the new design has an expansion pin In the case of the power steering bracket - always check the bolts! In the case of the power steering leak - cut off & re-use the hose In the case of the CCV - you can replace with a cold-weather design In the case of the cluster & MID pixels - they used lousy pink tape etc.
The oddest thing is that each of the common problems happens for many years over a few models so BMW doesn't care.
All have stupid reasons for existing (see above).
Notice though that nothing above is related directly to handling and power (although rear camber is but that's not a flaw but it's designed in).
The point is that BMW *only* knows how to design a drive train. Almost nothing else is BMW good at designing.
The proof is in the list above - which if you own the E39 or E38 or E46 of about the same years, you'll know to be all fact.