I'm not really knowledgeable about movie ratings, so I'm assuming this would be like an ESRB's E10+?

Pretty much, only except movies can get away with more stuff due to not being interactive.

Also the movie's staff probably wanted to do this:

https://tvtropes.org/pmwiki/pmwiki.php/Main/AvoidTheDreadedGRating

To summarize it:

If a movie got a G-rating, teens and adults would avoid the movie out of spite (or think of avoiding it as they don't want the stigma of watching a "kiddie" movie). But if the movie went farther the other way (PG-13 or R), then kids would be banned from seeing it.

So the movie's staff went with a PG-rating to make sure the movie can be seen by everyone possible.

EDIT - Ninja'd.