Yeah I noticed that too. I'm always struggling with Space (my work only gave me a 128G MacBook :S ), and using DiskInventoryX I found that these wallpapers occupied a non-trivial amount of space.
This is especially weird considering Apple has been pushing HEIF so much which is mainly intended to reduce space occupied by images, really they shouldn't be this large.
My previous Mac was a 2018 model MacBook Air with 128GB SSD, and I soon discovered that 128GB was way too little.
Even the 256GB I have in my 2020 model MacBook Pro M1 is a little bit on the short side tbh.
I have a 1TB external m2 SSD with an USB-C enclosure, but I only use it when I really really need to because it’s still a bit of a drag to have it sitting on the side and taking up one of the two ports.
If I could afford it I would probably go with 1TB internal storage. But even if I could afford it, I would then really really like to see such a MBP have 4 USB-C ports and not just 2.
Apple could pretty easily fix this by offering an M.2 slot in the Macbook. It's a shame they don't too: once the SSD dies in these Macs, they're dead forever. Not very "environmentally friendly" to me.
It's especially concerning for developers, since this mentality is sadly spreading through the rest of the ecosystem. If your Mac has a 128 gig drive and you install xCode, you'll be left with a little over 20 gigs of free space.
This is especially weird considering Apple has been pushing HEIF so much which is mainly intended to reduce space occupied by images, really they shouldn't be this large.