The argument from social workers typically being that if you can't find/make time for all the prep, where will you find/make time when your child is ill etc.
And I can sort of see their point. But it's a bit of a bummer if you lose income taking unpaid time off, that could benefit the children in the future. However, you need the prep to get the children, so it has to be done. Some employers are better than others, so always ask.
It's not like antenatal appointments, as they are to safeguard the woman, so it's a health and equality issue for women, whereas you're not going to put your health in danger because you missed an adoption meeting.
Even IVF appointments don't come under pregnancy appointments, and therefore equality legislation, until there is a pregnancy. Until then it's sick leave if you're unwell.
There's times when adoption is equivalent to pregnancy/birth. And there's times when it's not. After matching, I think it's right there are protections in place, but adopting isn't pregnancy, it just isn't. It's hard, don't get me wrong! Having done both, OMG, it's hard! But the health implications of pregnancy and birth, and the post natal period just aren't there.
If the placement ends, then you don't get the full leave for adoption, whereas if a woman's baby is stillborn, you do get full mat leave. And that is fine. Equality doesn't mean treating everyone the same.