In 1.13.2, retracted pistons and glass were not considered Block Normal Cubes.  

An example of how it changes gameplay:
Exit end gateways did not consider retracted pistons and glass as valid spawning positions in 1.13.2. Now they do.

What should happen:
Retracted pistons and glass shouldn't be considered Block Normal Cubes, and an exit gateway should not consider them as valid spawning locations, just like with extended pistons.