This quote makes me suspect you have also read Storms of My Grandchildren? At least, that’s where I learned about this stuff. A couple of other salient points from that book:
The IPCC projections of 20-50cm sea level rise are based on models that have the ice sheets growing. This is based on the fact that increased humidity means more snow, which is true, but it fails to account for subtle effects like changes in surface absorption as the ice melts, and changes in glacial friction as you note. So that 20-50cm is from thermal expansion and the loss of isolated glaciers alone. Remember that the IPCC was a collaborative effort that left out anything where there wasn’t total consensus, and “the ice caps are gonna melt all the way off” may have been a bit difficult for some people to accept.
The geological record shows that the sea level has in the past changed as rapidly as ten metres per century, and that in response to far less rapid shifts in atmospheric CO2.
The geological record also shows, if I’m remembering correctly, that the last time Antarctica was ice-free the sea level was something like 72 metres higher than it is today. Given that the ice sheets are already disintegrating it appears that no further CO2 needs to be introduced to the atmosphere for this to happen again.