Hmmm - agreed, my way phrasing this is a little misleading; nevertheless, it's roughly right -- as per Chris King's explanation (ditto Cane Creek), the key point is that in a true 'integrated' design (there are several 'standards') the bearings themselves run in contact with/float relative to the headtube itself, not a replaceable cup, whether external (conventional) or internal (xero stack, other names) as used by Giant.
Consequently, virtually any play/misadjustment in the bearings will ruin not a replaceable cup but the headtube/frame, and this risk is magnified on a bike used off-road. It's too bad that Giant insists on using the term 'integrated' when they mean 'internal' -- apparently some other mfgs are doing this as well.
Seems to me that this is one of those developments that might have application specifically in road racing at elite levels (if you are a pro and bugger your frame, another one drops out of the clouds!), though it seems questionable at best, but just doesn't transfer to real world, daily use or off-road bikes very well.