Can this person see the messages i sent them?

TLDR: I messaged someone from years ago. The message status keeps changing from “sent” to “seen”. Does this mean they viewed my messages?

I wanted to text someone i knew from years ago and i followed them during that time period.

But you can only message people only ONCE and again if they reply right.

Well I messaged them and didnt get that notification and every time i open the app, their message status changes from SENT to SEEN but only for a split second. It wasn’t like this before.

So did they see my messages?