Yes I agree that prob 30 can be ignored for edto alternates, but it would not have been planned as an edto flight on that sector. Having said that this is where the problem lay, where an enroute port is planned for emergency purposes or whatever, and when you get there it's clagged in.
Perhaps risk analysis has been carried out when regs are promulgated and " what are the chances of actually having to use an enroute port and the prob 30 actually turns to fog? "