I think it's definitely worth considering expanding the leave time for people who adopt more than one child at one time. For sibling groups, there are jurisdictions where the adoption of sibling groups makes you eligible for more leave than adopting a single child.
I also think it's important to ensure that there's some funding for the supports that the parents need post-adoption. This would probably help encourage more people to adopt and also to adopt children who have special challenges, maybe physical or cognitive challenges. That support doesn't necessarily have to come in the form of leave from work, but it's also that there's support for helping that child along the way.
As I said, there can be added challenges, beyond attachment, to adoption, and some of them can be expensive. Providing some support in that way is important, and also ensuring that those supports are really available to the people who adopt because some of them really struggle to find them.