When little of a prayer period remains, one might suppose the required prayer is automatically identified, since no other performance seems practical.
The passage does not treat mere narrowness of time as a substitute for specifying intention. The legal possibility of other prayers remains analytically relevant.
Example: Someone praying near the end of ẓuhr time should still intend the specific obligatory prayer instead of relying solely on the approaching deadline to identify it.
The practical shortness of the remaining time is not identical to the disappearance of every other legally possible act.