That’s true and a fair point, the tutorial say “at least”, not “exactly 1.5”.
Space requirement is not always the same, it depends on what’s being processed.
Others with 1.5 were able to install, others were not.
Also, you are trying to install a lot of packages at once, and NOW you are on 3.3 which leaves about 1.7 free… you previously were on 3.4 with less free space, since 3.4 is “bigger”…