Though, when I first started going to an SSPX chapel, I was amazed at how many SVs didn't actually go to Mass but hung out in the basement and get into arguments with anyone who would listen.
I find it incredibly hard to believe that sedevacantists drove to your SSPX chapel in order to NOT go to Mass.
Our chapel, when it was filled beyond capacity every Sunday, used to have a fairly large meet-ups downstairs after Mass. My guess is that some of these guys turned sede at some point during their time there but didn't want to leave behind the Church's community. I never really got to know them that well anyway.
TLM has a higher percentage of attracting shall we say "intense" personalities. Some of these people aren't the most stable you've ever met. Just last year, I saw a man sitting on a bench across the street from the Church and he was visibly shaking like he was physically ill. I asked him if he was alright and he asked me if our priest had been validly ordained. I said yes, but he just sat there and didn't come in.
I'm only stating the facts, I can't answer for them!