"I would expect that the California records committee would want to give careful scrutiny to any reported hiemalis, regardless of the common name. They are, after all, very similar taxa. Surely you don't mean that the committee wouldn't check dates and details if it were named "Eastern Wren!" Also, its puzzling to think that someone unfamiliar with the split would report either the eastern Winter Wren or the Pacific as a rarity."
I was actually speaking to the situation beyond California, & to the confusion that may now arise not just for new records but for old ones as well. If someone unfamiliar w/ the date of the split sees an old record for 'Winter Wren' from a state or province where both occur, they may assume that it was hiemalis when it was not, or was not verified to (then sub)species. This is an even greater risk in the months following the split as there will be those aware of the split using 'Winter Wren' to mean one thing, and those not yet clued in using 'Winter Wren' to mean another. If hiemalis now had a different name, seeing 'Winter Wren' would immediately flag records both old and new as needing further review.
I find it sad that the committee states that it follows the naming standards outlined in the preface to the 6th edition, yet continues to fail to do so when splitting species. It's one thing to retain 'Red-winged Blackbird' for the widespread North American species when splitting the Red-shouldered Blackbird of Cuba; it's quite another to retain things like 'Winter Wren' or 'Canada Goose'.
Update: After reading Kratter's post (& thank you for posting here), I'd like to add a bit to my thought.
If I may quote the film "The Princess Bride" (& please note that this is not directed at Kratter, btw), "I don't think that word means what you think it means." What does 'Winter Wren' now mean? It means whatever the person saying it intends, but the person hearing will have to ask for clarification because it simply cannot be clear. 'Did you mean in the old sense, or the new split sense?' This isn't just about records committees (& I daresay it will be more than just CA's committee that has to deal with this); it's about common birders speaking to one another. Clarity of communication is lost for them as well, assumptions will be made, & misunderstandings will arise.
For the records committee concern, a different source of error is being overlooked here. How many entries on ebird for 'Winter Wren' will now be made that actually refer to extralimital Pacific Wrens? Those will never be caught now. Certainly there would (& will) be misidentifications regardless of the name used, but at least w/ a different name more people might become aware that a change of classification has occurred, & they might then be more careful in their observations. Here again, the birding community is not well-served by the retenention of the old name IMO, as birders in the East in particular may miss that there has even been a change.