I think you were being very naive thinking you could work during adoption leave with a child just knocking about the place.
You may have loads of energy and able to work after bedtime, I thought I might do that, but usually I'm catching up with life admin & housework if I'm not shattered.
That might be why the SW are questioning you about how realistic you are and have you actually looked after a pre-schooler on your own before?
I took a year off work (saved like mad for it) but my DC did start nursery 3 half days when they turned 2 a few months in.
SWs were thrilled, nursery is a good safeguarding tick, I barely saw the SWs the first year, but they talked to the nursery and knew AC was turning up clean, happy, well-fed & healthy 3 times a week, and the nursery also saw me - not quite as clean, happy, well-fed or healthy as the AC, but still acceptable 
I used the time to lie down in a dark room as I found motherhood a big shock to the system, but if I didn't I could have started work again, I truely missed work, but I was so overwhelmed with the life changes of having a child placed with me, I just couldn't think straight and be useful at work.
I year in, I now WFH 4 days a week, AC is in nursery those days. I occasionally have paid childcare at the weekends to catch up with work because I can't work late like I used to (I'm single and I have no family to help with childcare)