That, to me suggests, they are encountering all the factory GM spec 6277M (red coolant) vehicles with leaks because thats what they all have in them.
They aren't generally going to find cars with green coolant.
This goes back to a now decades long argument.
There is form over the claim that red dexcool can degrade a system once significant air has been introduced. Having said that, the same goes for any system that has had significant air introduced. The problem isn't the air, it is "why is it there?" That means wear and tear is most at play.
To completely flush an entire cooling system free of one type to introduce another type is going to be impossible for the home 'mechanic'.
To convert them over to green would be risky, because when they mix, the two types form a gel.
However, just stick to what has been used for well over a decade now and bleed the air out and all should be well.