Boundaries Game area boundaries became fixed once set, even upon later

I've run into an interesting behavior a few times, where the 16x16 boundaries for the level are set and become unalterable, even when later attempting to edit the level.

I ran into it again and decided to strip things down and to make a virtue of necessity.

So, if you look at predestination, you'll notice that B will treat the entire back part of the level (the front being what's in the foreground when starting it), within the originally set 16x16 boundaries, as one-touch attainable targets. B will even climb down the stairs to get there, something B will not do if a space is outside the boundaries. Normally, travel outside the level requires a transitional move where you maneuver B to the border between the bound area and the exterior, then a touch to the space directly on the other side of the border.

I had originally deleted two rows in the back to add two more up front, but I still kept getting a maximum area error. This kept happening as I removed row after row in the back. Finally I was down to six rows at the front, and decided to just go with it.

I'm sure this is old news to those who have been making levels from the start. From those of you in the know, how can one force the boundaries to be fixed in a particular place?

 

And there I was, thinking this level was too easy and not worth posting.