2014 Audi S3 Issue

I would imagine your clutch it’s starting to slip my friend.

Had the same thing on my 64plate MK7 GTI, had only done about 18k, with 230ps. There’s plenty of people that have had the same issue. Think the clutches are a bit crap. So made sure I went for the s-tronic (not that they’re bulletproof!) when I got the S3

Does sound like clutch slip, but what you describe is not typically the first sign of the failure, which tends to be slip between gear changes.
When doing very fast / aggressive gear change under full throttle, especially from 2nd to 3rd, I found that the revs started taking a short time to drop down from 6.5k to 4k rpm even with the clutch pedal fully released. This got steadily worse over a period of about 2 months to the point that the revs simply didnt drop at all.
Even in that state of wear it would not slip under conditions you are talking about i.e. in 6th at about 70mph and floor it, but it made using full hard acceleration through the gears impossible. Once it starts slipping the clutch plate gets much hotter than it should which only accelerates its demise.
Keep driving it for now and see what happens and if it does get worse then look at changing it.