保留 and 未定: putting a decision on hold or leaving details undecided
Distinguish approval placed on hold from an undecided date, without treating a pending decision as approval or rejection.
Holding off on judgment or processing
保留, read ほりゅう, means putting a judgment or process on hold. 資料が足りないため、判断を保留しました。 means that judgment was deferred because information was insufficient.
承認は保留になっています。 says that approval is on hold. It does not mean that approval has been granted or that a final rejection has been issued.
Details that have not been decided
未定, read みてい, means undecided. 開催場所は未定です。 says that the venue has not yet been decided.
日時は未定ですが、開催することは決まっています。 says that the date and time are undecided, but holding the event has been decided. Only the specified details are 未定.
Tracking the action and its scope
日程の発表を保留しました。 says that announcing the schedule was put on hold. It does not tell you whether the schedule itself has already been decided.
日程が未定です。 says that the schedule itself is undecided. Separate the object of a deferred action from the information still undecided.
Can 承認は保留になっています。 be interpreted as a final rejection?
Show the answer and why
No. The approval decision is on hold. The wording alone establishes neither final approval nor final rejection.