Which ones do you mean with these?
Generally I’d say it is more the road condition than the tyre’s fault. 
My experience is very limited, but gladly I’ll tell you of my TWO flats within ten years:
- The first one occured with an original Schwalbe Marathon - flatsafe tyre
and the penetrator was - believe it or not - a tiny single staple of poorest quality, in fact nothing more than a thin piece of copper wire
- The second was a Schwalbe Kojak @ 8,0 bar and one hard and thorn-like shaped stone which hit the tyre exactly midships - strike, even if the aggressor was smaller than a corn of rice!
I’ve fixed the first flat on road and took the second home (because it was very near) but it has to be sad that repairing a flat is on Strida much more easy than on most other bikes due to the single sided wheel mounts.
…and I remember clearly that we had back then another, pretty unexpected, problem while fixing the flat - we couldn’t find the perforation in the tube and there was no water source available!
Since then I’m carrying one of these little fellows in the toolbag:
https://www.simson.eu/en/product/simson-leak-detector/
Above mentioned will reflect my personal meaning about “flat-safe” tyres but after thinking about it I do in fact remember someone; Ferenc - a member from Hungary - told me a while ago that he’s using a Kojak inside of another tyre as an additional antipuncture protection!
He cut off the beads of the inner tyre I believe.
Anyway, if you ask me and you really want 100% no flats, there is just one feasibility:
You saw this one?