Insurance quotes are worked out purely on actuarial data from past claims.
Each element of your details and the questions answered go to work out your premium. So there is a chance that in the past, the claims made by people who pay for TPO have been higher than those who pay for TPF&T
That would increase the premium even though it doesn’t seem logical at first.
There are a few strange anomalies when getting quotes, my insurance is 20% cheaper if I name my other half as a driver even though she is younger than me and has 3 points and a claim on her record and mine is clean.
It went down about another 7% when I named my dad as a driver so he could borrow it occasionally