clearstream
(He, Him)
Thank you, I feel you and @Oofta explained the dividing line far better than I did.There's nothing about D&D that precludes stakes being made clear. I suspect at many tables they are not, but those are probably not tables using stakes/narrative-based "say 'yes' or roll the dice".
In the context of 4e play, if it's not clear to me what a player thinks is at stake in a situation, I speak to them to clarify it.
Marked differences between what, or whom?
If the player sees the situation one way - and hence declares such-and-such an action for their PC - and the GM sees the situation another way, I'm not sure why it is essential that the GM's conception should prevail.
I take it that you're describing play that is more about learning the GM's conception of the fiction (eg the GM has already decided whether or not Marlinspike Hall is patrolled by dogs). So the fictional position of the PCs includes stuff that the players don't know about because it hasn't yet been revealed to them by the GM.
If I'm wrong, then I'm even less clear about what you're saying than I thought!
In a game where players are explorers rather than authors of the world, "say 'no', and don't roll" is at times the right response to cases that still fall within genuine participation. That is because there may be things unknown to players, but known to DM. The stakes - whether narrative or simulation - are sometimes not fully clear to the players. Even so, players can make choices that adjust them: changing a "no" to a roll, a roll to a better DC or "yes", a "yes" to a roll, etc. This is the normal mode of D&D.
In a game where authorship is shared, mysteries are equally unknown to the group and as you say, why prefer the DM? Even so, the group must have something in mind that answers the question: "say 'yes', or roll?" It may be they cannot see that a declaration is valid, so as a group they might say "no" or as you put it require expansion to get to "yes" or "roll". In any case, this is not the normal mode of D&D.
In both these modes, I do not see the stakes as unable to be impinged upon by player choices. To me, some of the most interesting player or group choices are those that change the stakes in play. Including worsening them! Is it that you require players to commit to the stakes as articulated, or can they position themselves in the fiction in a way that could impinge upon the stakes? Maybe that is a more fundamental division?
As to whether D&D precludes the second mode. As written it does mechanically. An example being ability checks where players in most cases aren't empowered to call for one or set its terms. And as written it does narratively, casting DM firmly as storyteller. What is gained is much as @Oofta describes. Characters live in the world, without knowing everything about that world.