ICT4 to M1 is completely lateral and happens frequently. ICT4 is also considered senior although it does not have a strict one to one mapping with the senior levels of google (level 5) or facebook (level 5). ICT5 is extremely difficult to get to. most people get stuck at ICT4 and it’s considered a terminal level.
I do not have much information. Give the amount of reading I did from blind ICT4s are qualified enough to move to M1. My recruiter vaguely mentioned that.
Saying that if it is senior TPM with my experience of 2.5 years, if I could work my ass off and get to IC5 then I could aim for better roles at companies like Amazon. Opens a window for me to go to Amazon as SDM rather than SDE. Then I will have relatively less to worry about PIP. Of course all this is my initial hypothesis. Could go wrong as well.