My position is that it should be 10 years from the date of release.I am writing this on a mid 2015 MacBook pro that I bought in 2015 that is still usable. so I can say that is definitely possible.
I would challenge your position that they should support the product from the time that any customer buys it. I feel like they should support it starting from the date they release it. if you buy a 3 year old designed iMac, that's kinda on you. Everyone in 2022 knew that apple was moving away from intel. So if you bought an intel iMac, you already knew that the processors were being phased out. Apple officially supporting a 2019 design until 2026-2027 seems pretty good to me.
If you bought an hp it wouldn’t even work for that long. Note also that you can install Ubuntu on your Mac to extend its functional life. When I replace my MBP I will install Ubuntu on my old mbp.