There is a weight penalty, are dual ply tyres any heavier than a tubeless setup with loads of sealant chucked in?…who cares, we’re talking mere grams of weight here.
Sorry but, IMO, utter tosh!
Dual ply, 60a, wire, High Roller = 1075g plus tube at 150g = 1225g
Single ply, 60a, folding, High Roller = 690g
That’s over 530g difference. With an assumed SG for Stan’s sealant of 1.2g/ml you’d need to squeeze in 440ml of sealant to be at the same weight. Squeeze-in would be appropriate as I don’t think it would all go in :-)
Stans recommend 120ml of sealant, so even going to 180ml (“loads of sealant”) you’ll still be 300g lighter with tubeless – per wheel!!
That is very noticeable.
BTW I’ve never had the need, even with brand new tyres, to use more than 120ml.
So, as above, the answer is tubeless.