he's talking about when you become "too big". Considering that you're most likely not too big, you can maintain those gains as long as you have a good diet, continue working out and an overall proper lifestyle. This is actually true about all steroids.
The differences between the 'wet' steroids that make you retain a lot of water and the 'dry' ones such as Tren is that you will lose the water almost immediately post-cycle. but the muscle remains with any steroids, assuming you're not a "mass monster" and that you continue working, dieting etc. Of course, you will also need your hormones on point. Some people attempt to stop all the steroids they've been running for years. Not even a PCT. their hormones are getting greatly out of balance so it's obvious they can lose muscles (when you walk around with 50ng/dl Testosterone).