Legacy is a strange engine that isn't really related to them except that it's based on Doom and uses some Boom extensions. Because it lacks any way to define new actors, you need to use DEHACKED, which basically just allows mod authors to RE-ARRANGE frames (you can't create new frames) and re-arrange Vanilla Doom actions.
Legacy is not simply a strange engine. Back in 2000 when I first joined the online DooM community Legacy was THE premier DooM source port, and ZDooM was a distant second. Legacy was the best at the time, and that is why I became so attached to it.
Unfortunately, Fab and Boris, the original developers of Legacy, left the project and development on Legacy stagnated and ground to a halt, while development continued on ZDooM, allowing ZDooM to catch up to and eventually surpass Legacy over the next few years. Remember, if you use features such as 3D floors, water, coloured sector lighting, or player skins in ZDooM, these features all came from Legacy. In fact, at one point I asked about a problem with the changing colours in player skins and the answer I got back from the ZDooM team was they could not fix it because the code for skins was taken directly from Legacy, and they didn't want to fool around with it.
The reason Legacy seems like the odd man out today is because while its development stalled, ZDooM's continued, and so many other project, such as Skulltag, CSDooM, and others started being based off of ZDooM rather than Legacy.
Legacy never had a DECORATE lump. Way back in 2000 (before the DECORATE lump even existed) I requested the Legacy team expand the thing and frame tables. This would have allowed users to add new monsters and decorations via DEHackEd, essentially functioning as a version of DECORATE. Sadly, this request was ignored.
As noted earlier, I did figure out how to hack into the Heretic tables that were hidden below the DooM tables and use them to good effect.
However, now that the project has been switched over to GZDooM, the custom hack editing I was doing no longer works, and had to be removed.
That is probably why the changes Strife made no longer work.