Most good quality OEM coolants contain the additives Sodium Silicate, Phosphate and Molydbate, in addition to Borate and Dextrin. They are not all listen on the data sheets as they are not all toxic and for some reason are not listed in the ingredients list either. Now go look up which one has a side effect of helping act as a sealant, because I forgot which one it was in the Volvo and Merc OEM coolant, it is not as good as a true stop leak but it does make a difference, as does adding a raw egg whilst the engine is running!
For cheaper cars they just use a factory fill stop leak in many cases as they don't want to use more expensive coolant, but the better manufacturers don't expect an owner to need to top up coolant or oil in between services, so they tend to use better coolant and oil seals.
Adds fan: Bars Leak Gold powder is the same stuff.
I just knew they would figure out what a great additive Gold powder is, first NASA put it in rocket engine oil as an anti wear, then the Chinese sell it as a snake oil additive and now Bars has thrown a few grams in their stop leak!