The Rock School approach is very different to classical. It's clearly aimed at the skills needed to play with other people rather than the traditional approach of sight reading, scales, harmony etc etc.
It's not worse, it's just different and it might not be what you are looking for.
Surprisingly Rock School also uses tabs even at G8, but of course all the rhythmic information is in the trad part of the sheet.
But then again there's differences between Trinity Rock School and RSL Rock School.
Personally, I'd have a chat with any local double bass teachers in your area. You are not looking how to learn how to play bass guitar - you can already do that. But you want someone to teach you the things you don't know - really the academics of music. Sight reading etc.
Then you can play any piece of music ever put in front of you and never have to ask if Tab is available.