architraves??

[Kastar UK]

I have an idea stuck in my head which I havnt tried yet. Remove the architrave and mitre the tiles with a small return to meet the frame around the same line the arch would start. Then Silicon around for movement

Your relying on the door frame being absolutely true without bows in the frame etc .
A brand new frame you have installed yourself have options to finish but still end of day is wood , can start growing again
A general rule we remove the arcs , rough cuts past the arc line , then get our new arc rebated so sits nice and covers the cuts