Totally understand you wanting him home with you for as long as possible!

As far as I know your company's policy is pretty much standard re both parents taking leave at the same time.
My understanding is that it only relates to parental leave, ie only one parent at a time can take long parental leave - but I don't think that relates to holidays, and I wouldn't think it relates to partner leave either as that is offered by his company, kwim?

In any case he should be able to take the partner leave & then any annual leave owing. I think the question would be more if his company is happy for him to string it together like that (yeah they should but some wouldn't be..)

And keeping in mind...if you are on Maternity leave for 12 months do they expect him to not take any annual leave at all during that time? That would be unreasonable... so for that reason too I am thinking he can take his annual leave whenever he likes...

ETA not sure what state you are in or what workplace laws etc apply to you both but check it out online. For eg I looked up QLD gov workplace relations for my DH when he was told he may not be able to take leave (grr). Not the same situation as you, as I am only casual, but useful for us if we need to make an argument to his work...

HTH