as a timecode slave the daw should or could be aware of what will happen because it can precalculate all the tempo changes for the entire song length.. But only if the developers see a reason to do so..
The good old atari program Notator form c-lab was allready able to do what you ask for.. but you had to render a sync refference with all the tempochanges first.. a modern DAW should be able to do this automatical in the background..
But as we all know..Ableton Live is "different"
With live such an algorythm probably wasnt applied... So you cant call it a bug..just some missing knowledge regarding timecode syncing.. MAybe just forgotten to develop for the case of tempochanges..
Was Live 1 able to do tempochanges? cant remember.. but i think tempochanges was a "new" feature at one point...
MAybe the missing feature is related to an initial one tempo concept?
I guess you should put in on the wishlist or claim this to be a conceptional bug and put it on the buglist..
However
On my machine timecode is not working at all.. and reffering to the bugforum Ableton dont considers this as a bug..
So good luck with your problem
MAy i ask on what system you are running? Mac/ Pc, which OS?