Ah, yes, that may be one point in favor. I think they are but it may not be a given in all cases. For example if they have positive rake maybe? wouldn't lend themselves to being supported inverted on flat of toolholder datum. Maybe someone who runs them can answer. Ultimately I guess its $/cutting corner. I find them to be very long lasting, but varies my work & materials.
TNMG has no rake/0 clearance angle to the insert, that's what the N stands for
I have one tool holder with a tnmg insert, the insert is very big, you would have to have one heck of a big boring bar to use that style of insert in it...unless they make a smaller tnmg than the one I have