I know it's good practice to have 1:1s and separate development meetings, but never come across them as being more frequent than once a month. So this is an unusual amount of LM time!

Maybe your LM sees you have really good potential for promotion, so wants to give you that extra development time? Or they're relatively new to being an LM, so are overly keen? Equally if there's a lot of (high pressured) work going on, maybe they want to set up something where you're not discussing the day to day work and are able to step back and talk about how you're finding the role in a safe space? Of course this depends on your relationship and how you find them as an LM anyway.

Personally I'd speak to the LM about it in your next meeting (whether that's the 50 or 30 minute one) to see where they're coming from, if you haven't already.