Re: St. Andrew's?

You are right, the use of the apostrophe would suggest that the stadium belongs to St Andrew.

No apostrophe “St Andrews” would suggest that there is more than one St Andrew.

Use of the apostrophe is very inconsistent - a quick search shows that St Paul’s Cathedral uses it, St Davids in Wales doesn’t use it, St John’s Wood uses it etc. I found one article that said that the town of St Andrews in Scotland doesn’t use it because the town originated before the introduction of the apostrophe into the English language.

Confusing but would seem using the apostrophe in the stadium name is correct.