Isn't it pretty much up to the founder and board whether you get diluted (and how much) in the future, and whether any number you see there continues to be accurate (for your own purposes, or others in the table) or not? And unless you're one of the top people at the company, your net worth is going to ride largely on how much of a success the company becomes, not your particular % / exact small share of it.
The VCs and next funders care about the exact numbers. What would you do, use it to negotiate more?
I suppose you could take it as some indication, but it's by no means some kind of binding assurance of the future. This is a thing I have a fundamental gripe about SV startup practices -- there are a lot of things associated with being employed at one that have the appearance of legal obligations and securities regulations to the novice eye, but under the surface they are not at all, and you are largely at them whim of whoever owns the company. The value of your options could evaporate in practice, even though you hold "100,000" of them (either through decline in company's future, or active dilution, or the CEO just doesn't like you).
Or am I exaggerating what I feel after a decade in the area?
There are a lot of questions that people ask, where I feel, is it even meaningful information you would act on or are you trying to feel better about something? (see all the useless 20-year-old-something comments/questions in threads after some company CEO announces the possibility of layoffs... "Can you share the exact formula by which people will be laid off?" "Why are you doing this in successive rounds and not all at once?" etc. etc. What would you do even if you knew the answer?? )