I am not disputing that small baths are made. I pointing out that most of "us" do not have one installed. If you walk round the sheds or bathroom showrooms, most of the baths on display are not 80-100L ones either. Hence this is why we have trouble believing your claims for the average bath size.
I use a combi, and tolerate it - it is a compromise that suited my needs.
However, you are attempting to divert the discussion. We are not talking about the type of combi that "millions" have installed.
An alpha with combined storage is not a "standard" combi. Its dynamic performance in the delivery of water is different. With that difference comes a number of operational procedures that the operator will need to put in place to get effective use from it. The same is true of a conventional combi, however the procedures are different.
Vis bath filling procedure:
Adequately sized stored system:
Turn on hot and cold, adjust temperature to liking, come back when bath is full and turn off taps.
Combi:
Turn on hot tap, wait for water to stabilise in temperature. Reduce flow rate until desired temperature reached, come back when bath full and turn off tap.
Alpha:
Start as per stored system, wait until hot flow rate reduces, turn down/off cold tap until desired temperature balance is restored.
For the combi or alpha (and equal) this is not rocket science, and just requires a bit of training for the user. It may also require some instruction for guests.
However it is worth pointing out for those looking at a product like the Alpha, that they will not get the simplicity of operation that a correctly sized stored water system would provide - it will in fact be like having a mixture of combi and stored water system, which is not supprising since it is.
As a starter perhaps, but we are talking bathroom suites here.
At last - that is was my point exactly. It will drop off in flow rate, hence you need to remember to turn down the cold tap when this happens or you are going to get a tepid bath. Either that, or you need to do some trial and error to work out a starting temperature for the mix that is actually too hot, but which will mix down to an acceptable final temperature when the slug of tepid water is added toward the end.