BTW, a bit of a gray area I guess, but if you need one or two wheels you can go on Ikea "replacement parts" page and order them there for free. Also (cheap) drawer slides and other ikea hardware.
I don't know, on the survey for spare parts where it asks "what do you need them for", I just mark the upgrading/strengthening ikea furniture box. So I guess they're fine with that? I have some Ikea stuff and I have ordered some extra ikea corner braces as a replacement part for "strengthening" a closet once, and noticed they offer a ton of stuff... So for example, I also swapped the casters on my Markus chair cause they got a little squeaky over the years.