CR — Two entry criteria cannot be connected

If you have a task contained by a stage, you cannot connect an entry criterion from the stage with an entry criterion from the task.

This could be handy if a task should only be available if the stage was entered through a specified entry criterion.

Only a exit criterion can be connected to an entry criterion based on this sentence on page 26:

SentryRef, if specified, MUST refer to a Sentry that is referenced by an exitCriteriaRef of the PlanItem that is referred to as the sourceRef of the PlanItemOnPart.

Do not remove constraints on sentryRef

You refer to the semantics of sentryRef in table 23.
This is a very specific, though useful situation. It is the CMMN counterpart of what is aka “state transition”: when an event comes, and one state (here stage) is exited, another state is entered, in one consistent (transition) transaction.
We should however not remove the constraints on sentryRef, and do as if any Sentry can then reference, via its OnPart, to another Sentry. Because that would not make good semantics.
What we provided with sentryRef is a specific, and therefore special (exceptional) situation. We should not make the exception the rule.