It's not a good reason, but their reasoning is probably something like, "Having tutorials on the official page of the older app maybe confusing for people looking for help with the new app"

I do understand why they did it, I just think it's a bad reason.

But thinking back, I never saw tutorials for Version 1 of the software there, so I guess this isn't new.

Still I think they should have a public archive in their own channels. They could change titles and descriptions to explicitly say it's an old version, wouldn't cost them anything but a few minutes.