First: Potter's pathway was long and hard and she has excelled.
Second: That doesn't mean that 'go north to Leeds, young man' is the only pathway, especially as it's in decline (from a very high point, discuss) and the ascendent is Loughborough/Nottingham (no idea what you mean by "home county" btw).
Third: Potter was an excellent swimmer all through school so after her Rio 10000m she had a sound foundation for transitioning into tri. Milner stopped proper swimming before he was 10 so he's had further to go, but really is getting there in the water but then at the highest (WTCS) level with the front pack really pushing, he's found out. Bear in mind Yokohama was about the 6th standard distance race of his life!
Immediate future: Will be interesting to see if he briefly pivots to the 10000m/5000m on the track this summer to see if he can get sub 13:20/27:20, which he sounds confident about (World Tri podcast after Miyazaki, back in November. The UK 10000m trials are next weekend! The 5000s are in late June.
As for LCB and Stapley neither have the potential to run fast enough for short course success (GBR top flight). You might reasonably consider BriTri did Charles a favour by saying thanks but no thanks: get back to long course. After the Leeds cameo she immediately dominated the 70.3 worlds (St George) and the rest is history.
As for Stapley, he could enhance his chance with a performance in Cagliari but that loss of time on the run will be an unattractive proposition on Leg 1 in August, however you cut it. As soon as selections are made (in 17 days), he needs to go long straight away and stop faffing around. He has his Taupo start. Use his form to show those middle distance European chaps what's what.