I’m not saying you can’t learn this way. I’m saying it’s not practical for most people. Many people who would fail this way would succeed other ways. Reading man bash as primary learning material will lead to failure for 999/1000 humans.
I spent 10 years avoiding awk, because every time I typed 'man awk' I was overwhelmed by the GNU monstrosity. Then I found the man page for the plan9 implementation of awk (http://man.cat-v.org/plan_9/1/awk) and learned the language in fifteen minutes.
Rather, info manuals are GNU's official (self-invented I think) documentation system. They make manpages only because of their popularity, but they direct you to the info pages for more info. When other projects have too much documentation for a manpage, they split it among several pages, like perl, openssl, zsh, git, borg, btrfs, etc. Personally, I like both, and wouldn't rank one above the other.