I take the view that the guarantee is there for faulty wines. I’ve used it twice in over ten years for that. Only other refunds have been missing or broken wines (not going there again!).
Don’t like it? Not ‘good value’? Don’t buy it again…but I think it would be a bit open to abuse by some if a refund was given on a regular basis. Price just goes up for all when that happens.
Regarding the reviews of this wine, very nice and 3 stars don’t imply a bad wine. Whether it’s good or bad value for money is a different question. Some people explicitly include value for money in their stars. Some do it implicitly I think, or maybe don’t realise.
I probably do it too - but I very rarely give a 5 star and I have to say that a sub £20 wine would be unlikely to get it, just because I can’t recall encountering one that merited it. Rapsani Terra Petra probably did, but it’s now over £20. 5 stars should be very sparing IMO or they become devalued. In the same way that Suckling and Halliday devalue 95 point wines.
I sometimes give 4 stars and make it clear it’s really 4 and a half, or why it wasn’t five.