I'm sure this has to do with a couple of things. The collection of random vocabulary in various languages has in my head gets larger and more varied every year, so I have a lot more points to start from. Also, I seem to have much less inhibition about launching into a language I kind of sort of know than I used to.
I say this with the caveat that I continue to know jack all about grammar in most languages other than English and Mandarin, both of which I picked up more or less in infancy*, and have forgotten most of what I learned about grammar in French, which I actually took classes in. I don't particularly learn languages via formal grammar rules, which probably also has something to do with the way I use the languages I do.
Nonetheless, I keep having experiences where I am confronted with a situation where I have a specific need to say something in a language I don't actually know and some words will fall out of my mouth, and be understandable enough to get me a useful response. Sometimes it's even correct!
I'm generally surprised by this after it happens.
It's not as useful as it sounds because I'd like to be able to come up with something to say on command instead of just having words fall out of my mouth unpredictably, but I'll take it. Besides, people claim words randomly pop out of my mouth when I'm speaking English and Mandarin, too. :)
*In both English and Mandarin my usual response to someone asking if some sentence is gramatically correct is to say it to myself to pass it through the "sounds right? sounds wrong?" test, and then backfill to try and apply some rule I learned sometime. Formal grammar and I have a somewhat fraught relationship.