It seems like the Comparable Call definition works against purpose in this case. None of the definitions in Law 23A really fit.
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has the same or similar meaning as that attributable to the withdrawn call
Other than showing spades, there's not much similarity between opening 1
♠ and responding 1
♠.
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defines a subset of the possible meanings attributable to the withdrawn call
This is the opposite: the withdrawn call's meaning is a subset of the replacement.
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has the same purpose (e.g. an asking bid or a relay) as that attributable to the withdrawn call.
This is mainly intended for artificial calls, so doesn't apply here. I don't think we can consider "suggest spades as a denomination" to be "the same purpose" of both bids and ignore all the other details of their meanings.
This seems unfortunate to me. It feels like we should allow west to respond 1
♠. I don't think the UI issue is relevant, as East is required to ignore the UI and bid as if West is only showing 4+
♠ and 5+ HCP. If he were to make a 3-card raise when there are other LAs, or jump to game with a minimum opening, those would be UI violations. But if they end up in game via a normal route, which would be likely with the given hands, we get a normal bridge result and "no harm, no foul" should apply.
But it doesn't seem like the Laws as written allow this.