[FIOS] using my own router to ont and using actiontec for cable boxes only

I was told by a FIOS service tech that I could use my own router plugged into ONT ethernet port while keeping the FIOS router on the coax for cable box functions only. I can't find anywhere were others have done this on the internet so, I'm asking if this is true? I have found many post on other ways just none with keeping both routers going to ONT.