Service contract on my Weil McLain furnace - too vague?

is this standard verbiage for a furnace service plan or would I sound like a pain in the neck if I made them list out all the parts that fail from normal wear?
" that fail from normal wear or breakdown during the year are also covered."
I don't want to seem like I don't trust the company but they way this is spelled out seems to put the company in the position of rejecting the service plan for anything they want - or are the parts that normally wear obvious?
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