Notepad was just a wrapper around some default win32 controls. Judging alone by exe size is not right, although probably a “statically linked” notepad would still be smaller than emacs
It is a flag that says whether the loader data is initialized or not.
The layout of PEB_LDR_DATA “leaked” long time ago in public PDBs.
More context: It has nothing to do with debugging. However, if you attach to the process early enough, you might see the flag as 0 and eventually it would switch to 1. That is probably what threw him off.