PPE at Oxford requires no certain A Level subjects, History and Maths are 'helpful' (not even 'recommended').
So technically you are at no disadvantage; but the tutor is right in saying that the vast majority of candidates will offer at least AS Maths.
They will have an advantage over you in terms of being able to do most (if not all) of the maths that 1st year PPE requires, and hence tutors at interview will suppose this aspect of the course will pose no problems.
You just need to show you have the aptitude for PPE, and in that show that you are capable of understanding the mathematical concepts required.
Once you get to Oxford, if you don't have Maths past GCSE it just requires a couple more lectures and perhaps more time spent on your Economics till you reach the same level as others.
Every year candidates are admitted who don't have Maths past GCSE, which shows tutors can look past this.
So will it be a disadvantage? I don't know...
You'll be at the same disadvantage as someone offering no essay subjects (History, English etc) because from the Pol/Phil and even Econ viewpoint this is as much an issue as having no Maths.
It's not really a useful reply I know. I did A Level Maths but one of my fellow PPEists in my college didn't do AS, nor did another one I know of in the year above me. Economics is just one third of the course after all.
If my Philosophy tutor is to be believed, there is an annual debate as to whether AS Maths should be a required subject. An idea vociferously opposed by the Phil and Pol tutors who question why Economics should dominate in such a way...