Dalinar's situation involved memory, which we knew from very early on. Taravangian's doesn't, so we have much less reason to suspect that his impression of the interaction is wrong.
When Dalinar met Cultivation, if I remember correctly (I don't have Oathbringer with me), he first met Nightwatcher, and then Cultivation intervened. When Taravangian was complaining that Nightwatcher didn't forgo her traditional bane even though what he asked for was the capacity to save the world, he would probably have mentioned if some third party interrupted.
Of course, this doesn't mean that Cultivation didn't meet with him pretending to be Nightwatcher the entire time, but that wouldn't be the same situation as Dalinar.
Taravangian's situation is so different from Dalinar's that I don't think it's very likely that Cultivation intervened. It would certainly be interesting to ask Brandon how many of the 'Nightwatcher''s bargains were actually Cultivation, though!
Edit: Wow, when you forget to post other people post much more interesting things!