Lets not forget that ETOPs is purely a planning tool so once past you EEP there is no requirement to divert if the weather goes below minima as at its most basic form you may not have the fuel to go anywhere but you destination or nominated alternate should an engine fail or depressurisation occur. It doesn't mean you 'shouldn't' divert if the weather drops below minima and you have enough gas on to consider other options. Of course you keep updating the weather to keep an eye on what is happening.