Ultimatums......Do they turn you on?

I'm trying to figure this out. Assuming the D/s relationship gives the Dominant the right to "train" the submissive by rewarding and punishing acts of all kinds . . . If the dominant person expresses the wish that the sub do something, that wish becomes an absolute obligation for the subordinate, how can ultimatums arise at all? Wouldn't then, everything the dominant says or expresses become an implied ultimatum of sorts?

The dominant would never need to express the possibility of punishment since the decision to punish or reward the sub falls entirely within the dominant's discretion. The sub already understands that dominant's right to give rewards and punishments are the foundation of the entire relationship.

While the sub may be conditioned to expect one or the other based on whether they fully comply with their dominant's wish, the dominant still is not bound by the sub's expectation. If the dominant had to discipline or punish the submissive for every infraction, the roles would reverse. The submissive would control what the dominant does by acting in ways that require a certain response.

AND that would be totally fucked up!

Ultimatums are generally along the lines of 'If you don't do X, I'll do this'. The difference between ultimatums and D/s is generally that there are negotiated limits with the latter, and not necessarily with the former. I've never really encountered the idea of ultimatums used in D/s, as normally both parties know where their respective limits are regarding things, and any desire to change those limits is ordinarily discussed rather than coerced or pushed.