I don't know why this happens, but yes, it does happen. I just did a quick double-check and it still happens. Even if I do the equivalent in JXA instead of Applescript.
My only solution is to move to using Local and Instance variables everywhere. And in fact, I'm in the middle of working on that. It's a long process, which I'm doing litle by little.
And, in fact, that's one of the reasons I wrote my Variable Inspector Prompt macro. I can list all global variables, sort by size (if I want), and hunt them down in KM using one of the tool buttons in my Prompt.
If you decide to check it out, I'm about to upload version 2.0.2 which fixes a display/scroll bug when you have large dictionaries. But if that doesn't really affect you, then the current version 2.0.1 will work just fine.