Wrong ruby version specified in gemspec allows installing gem version that won't work

[Nakilon]

SyntaxError (/Users/nakilon/.rbenv/versions/2.5.7/lib/ruby/gems/2.5.0/gems/infoboxer-0.4.0/lib/infoboxer/tree/table.rb:35: syntax error, unexpected ']')
          rows[1..]

There was a big commit recently introducing lots of modern features.
But .gemspec says:

  s.required_ruby_version = '>= 2.1.0'

Either this should be corrected or... I'm personally not sure that omitting -1 is worth losing compatibility.