Why does Ruby Gem 3 install gems to Ruby 2 directories?

I have just installed the tmuxinator 3.0.5 ruby gem with gem 3.2.5 and the --user-install parameter, and to my surprise the gem was installed to ~/.gem/ruby/2.7.0/bin/.

Is this a misconfiguration? Will it bite me in the future? I had a quick look at the environment and haven't found a variable that could have done this. Or did I just misunderstand something? I assume that the version of gem goes in tandem with the version of ruby, at least regarding the major version number, but I might be wrong, as I'm not familiar with it.

I have checked the version of gem by running gem --version. This is on a Debian Bullseye based distribution.