for if and when?

Question

According to Oxford Dictionary, if and when means at a future time. But why did the author use for in front of if and when, which I think is redundant?

Remember that patience is always of the essence. If an apology is not accepted, thank the individual for hearing you out and leave the door open for if and when he wishes to reconcile. Be conscious of the fact that just because someone accepts your apology does not mean she has fully forgiven you. It can take time, maybe a long time, before the injured party can completely let go and fully trust you again. There is little you can do to speed this process up. If the person is truly important to you, it is worthwhile to give him or her the time and space needed to heal. Do not expect the person to go right back to acting normally immediately.

Change Your Future, Now!: Questions, Reflections & Answers

Answer 1

The preposition "for" in this case is not redundant. In the paragraph you quoted, it indicates that there is a purpose to, or a beneficiary of, the action of leaving the door open. To use a simpler example:

"Leave the door open for reconciliation" is correct. "Leave the door open reconciliation" is not. "Reconciliation" in this case is the purpose of leaving the door open.

Without the word "for", the phrase "leave the door open" and "if and when he wishes to reconcile" have no proper connection.

EDIT: Per gotube's comment below, I think a clarification is needed. A sentence like "Leave the door open if and when someone wants to reconcile (but not otherwise)" would also be correct grammar. However, the intended meaning of the quote is "leave the door open so that he may reconcile later on, if he feels like it." It's describing the purpose of leaving the door open, not the condition under which leaving it open is allowed. Thus "for" is required in this particular case.