Based on previous comms it's up to the individual to comply with the rules so I don't think they will - two in my 'ticket bubble' are in T3 and not able to go. They also can't be 100% certain that the STH is living at the address registered anyway (works both ways obviously) - Uni students being a good example who might be living away but STH recorded as home address.
Precisely - my son has lived in London for several years, but his season ticket is still registered at my Brighton address. If he were to come to matches while being in Tier 3 (and I would stress that he certainly isn’t going to do that) the club would be none the wiser.