I actually see it the opposite: basements make the ground floor not being the same as the first floor even more confusing.

For instance, in the US you could have this building:

Second floor (2)

First floor (1)

First basement (B1)

Second basement (B2)

2 upper floors + 2 basement floors = 4 floors total (easy math).

I could see an argument that when counting whole numbers from positive to negative, we normally include "0," so then wouldn't you have a 2 floor, 1 floor, 0 floor, -1 floor, -2 floor? But that's not how counting physical objects actually works, because it then implies that the ground floor (0 floor) doesn't exist, and the basement floors are somehow anti-floors? Like they exist in the upside-down or are made of antimatter or something. So I don't think the inclusion of a "0th floor" makes sense even with basement floors.

Room naming isn't a problem either, because you're not actually counting the rooms: the existence of room 200 doesn't require the existence of room 199, after all. So having a "000" series of rooms is not only unnecessary, but could cause confusion because it looks like an error (like "room 004" was supposed to be "room 1004" but the "1" fell off). Prior to computers and the need to label files "001" so the computer would sort them correctly, we didn't label things with unnecessary leading zeros like that, because any human sorting things knows that "2" comes before "18" in a series, not the other way around. It's not like we label other similar things, such as buildings, with leading zeros: we wouldn't say someone lives at "0040 Baker St"... they live at "40 Baker St" or "400 Baker St" or "4000 Baker St" or shudder "40000 Baker St." (There actually is a city in the US--Portland Oregon--where because of geography they used to label a small number of addresses as "Southwest 0XXX Whatever Ave," but the leading zero caused so much confusion that the city designated a whole new category of "South" for a relatively small sliver of land just to resolve the problem... They had already done so to distinguish "North Portland" from "Northeast Portland," but again due to geography that was a substantial amount of land so it made sense for this "fifth quadrant" as it was called to exist. If this all sounds nonsensical it's because it's really hard to explain quickly and without a map.).

I normally wouldn't care so much about this topic but I found the ground floor/first floor thing really confusing and frustrating when I traveled abroad, so now I have opinions! Also I'm sick today and this has been a great distraction from how icky I feel.