I don't think you should have much concern about them 'rolling' and 'keeping together'(?), but that doesn't mean i think you should buy them. As GB points out, budget tyres, which is never a good thing. Those four palm-of-your-hand sized rubber patches are the only contact between your car and the road, so trying to save money here is not wise. Also, these being after market alloys, rather than genuine VW ones, mean the 'diamond cut' finish is likely to deteriorate much faster than normal. The lacquer will start lifting leaving that horrible milky white patches. I'd also be interested to see the inside of the alloys, to see how much balancing weights have been used. My only experience of buying a set of after market wheels/tyres like this was as a birthday present for my Dad. When they arrived they had a huge, and very noticeable amount of weights. I don't know if this was solely due to them being cheap wheels with cheap tyres, but it certainly would make me wary of buying another set.

I think i'd be looking at what else you could fit, maybe a set of used wheels from a Golf GTI, onto which you could fit a decent quality tyre.

You say in the title its a 2017 Polo GTi but you say in the first line of the post its a new car, cannot be both can it.

All Polo GTi's come with alloy wheels as standard thus since it appears to be a used car its clear that someone has either changed the wheels or stuck GTi badge on a non GTi car.

Whichever it is why on earth did you buy it, plenty of unmolested cars out there to buy.

I did the opposite two years ago, my car came with 17" alloys and I switched for 15", the same size as the spare that was supplied with the car. Reasons - two.

Firstly, better ride.

Secondly, much much better choice of tyres and at considerably more wallet friendly prices.

I can't remember any impact on handling, but I don't push when driving; if there was any I quickly adjusted and become used to the new normal. Of course having different tyres on the car gave a new driving experience anyway.

The alloys were purchased second hand from an authorised dealer, a fitting I knew from the brochure and the supply of full size spare would fit my car - including the brakes.

I did check the impact of a different wheel size on the speedometer and odometer, and it is very little. https://www.willtheyfit.com/

Some additional background information here.

https://www.honestjohn.co.uk/askhj/answer/49667/can-i-change-the-tyres-on-my-peugeot-308-sport-for-a-smoother-ride-

This is the second car I'd done this, then I also fitted original manufacturer size alternative alloys to match a smaller but still full size spare as supplied with the car.

I did something similar on my Mazda3, swithcing from the original 16in OEMs to 15in (still the OEM design) when they corroded an at least one needed replacing, with the tyres about a year at most away from my usual replacement date.

Far, far cheaper, looks fine, better ride and the tyres (from 55 to 65 profile) are also about 20 - 25% cheaper as well.

Obviously not what the OP wants here - and I suspect they just want an opinion about whether said ebay offering is legit or not, as I would suppose the Polo GTI comes on that size rims anyway - they are probably just after a different design.

I'll leave that to those who have more knowledge on ebay sales, as I only use it occasionally and only a couple of times for car-related stuff (genuine branded consumables from a reputable seller with a proper business address).

I agree that many 'warm hatch' cars can get by perfectly well on 'standard' sized wheels and tyres, grip / handling wise, and be of much greater benefit in terms of cost, longevity, comfort and a reduced susceptibility to damage.