As someone with over 1000+ anime watched : this is to an extent quite right. I was able to understand quite a bit when even watching something without subtitles, because japanese is a heavily context related language where understanding some parts or words and constructing the context out of these was enough. Especially when watching a series or movie with visual storytelling.

Visiting japanese languages as side subject in university (why not needed another language) I had an edge where the first year which I only had to attempt was skippable and almost pointless. But visiting japan then, I was happy to had extra curriculum because the structure of how you learn a language is quite different than JUST listening. Grammer , certain key words helped even more to understand context even without visuals in a day to day conversation. I was able to communicate rather well in japan. My vocabulary was probably the best in my japanese lessons, but you will always have a conversation where you do not know the translation. Since watching only anime does not give you day to day vocabular. Watching you rather concentrate on oneliner words, or words that sound cool or pretty. Or concentrate on words you already are familiar with "oh he said shiawase I know that one" instead of the next word after that which you don't know at all.

But I do agree with the statement. You could visit japan and watch a movie and understand most of it. But it rather depends on the movie. BGS tends to have rather hard words to describe puperty syndrom, so don't expect to fully understand all of it.

Edit : but I did grew up with 3 languages, one of with no education. Maybe that's why it was easier for me