I taught EPQ for 8 years and was subject lead for 4.
EPQs are brilliant for teaching the skills that will set young people up for university: researching, sifting information, referencing, extended writing, time management, presenting their findings etc. They can be great as a "try before you buy" option for university courses which do not correlate exactly with A levels. As others have said, an A or A star grade in EPQ can lower offers from some institutions. Even where this is not done formally, on results day every year, we had students getting into their first choice institution having missed their A level grade(s) because they had an A or A star in EPQ. Last summer that included a very niche artefact which was connected to a very niche course at Cambridge. The student dropped 2 grades so their original college said no. However, another college took them because of the A star in a related EPQ. A couple of years ago, a kid dropped EPQ in y13, but following disastrous mock results, decided to pick it up and finish it. They got a B and somehow scraped into the course of their dreams.
However, if your student is ambivalent about their question or title, not very motivated or struggling with A levels, it might be better to drop it.
The key takeaway from my students, particularly after they have gone onto Higher Education courses is that they really appreciated the skills being taught in bite-sized chunks by EPQ supervisors, and this stood them in great stead when they started their university work.