I mixed many things, for the yellow red yes there are 2 mazes, here there are no gaps between the mesh because there just one frontier. For intersection of more than two frontiers there will be a gap when doing CatMull and Clark smoothing, except if you choose to not smooth the border. In order to overcome that I implemented a multimaterial CatMull & Clark, each face has a material (integer indeed), see this link.
For my maze I used Recursive Backtracking. It is perfect maze. See this link
I’ll be interested by what your mazes. I don’t remember seeing your work or an other name