Maybe your tires are more resistant to punctures.
Maybe you are in an area where there are few things to puncture tires.
Maybe you have had more seal with sealant than you think.
Where I am, there are several types of plants with sharp spikes on them. They are impossible to avoid, if you go where I go.
Yes of course there are lots of variables. But I got a lot of punctures when running tubed tyres. We live in a rural area full of prickly plants and farm vehicles spreading debris all over the roads. So I would say it’s a good test for puncture resistance. For that reason I do tend to run tyres that have a high puncture resistance rating (currently Pirelli Cinturato Velo). With a good quality sealant, these appear to be bullet proof. I certainly don’t see any need for a tube inside.