It’s lovely to see pics of high end work and I sometimes get involved In it but this is bread and butter stuff right here and I’m not ashamed to admit it.
Old lady having a hip replacement done and the old dear won’t be able to get her leg over.......the Bath. Popping a tray in instead and fighting with the space and trying to bond it to the deck so there’s only a tiny step. All good fun
You should have no issues tiling onto one coat plaster, not tiled onto it myself but have used it in the past as a patching plaster and recall it being pretty tough stuff, with a fairly open texture to it, a coat or two of primer and it should be right.
Aye my experience of one coat was the blue circle stuff from a bygone era, it was like chewing gum to apply, you could only apply it by troweling in one direction.
Will depend a lot on depth and areas to be coated backgrounds together with weight and type of tile to be applied.
There are lots of good fast setting patching mortars and plasters available also.