Personally, I hope radar never gets added. This is the only minimap I've found without it. This minimap mod is simple. It has a map. It has waypoints. Nothing else. Every map I've used that had radar caused much more lag than this one. This mod barely drops my fps, if at all.
I think he means lots of changes to the blocks/terrain (basically so that you can actually notice that the terrain changes in the minimap). It has been a bug in MapWriter at least since 1.6.4, maybe even longer, that the minimap cycles between different states of the world. Some sort of weird buffer duplication or something somewhere.
If the bug he is talking about is the same as mine, he means like say there is a forest. You then cut down the trees and build a house in their place. The minimap will start flickering between the old trees and the new house. I've noticed this bug before, but never thought much of it because quitting to the title screen and reloading the world fixed it.