I do think it's a bit of a daft rule, can a slot not be saved for the winners without someone else having to drop out?
I realise there's the traditional idea that 4th shouldn't earn the Champions League anyway but that's not really the point, the rules are what they are, and triumphs such as Istanbul 2005 were thanks to 4th place.
I think it's unfair - as you say, UEFA should reserve a spot for the holders and, when the draw is made and you see the nationality on the slip (or indeed any other table, etc, during the course of the competition) it should read 'UEFA' (or show their logo instead).
At least that there'd be a benefit (Everton into the Europa League, in this instance) rather than a drawback (Spurs dropping down a tier, despite qualifying fairly and squarely for the initial draws).
Feel for them really - would be absolutely gutted in the same scenario.