OP - DD1 started daycare after she turned 2, and for the first ? almost year, she'd just follow the carer she'd attached to round and not speak. She'd play beside other kids, but not really with them.
When I'd pick her up, they would be shocked how "alive" she'd come and how chatty!
It just took her a while to settle in - now she goes 2 days a week, and when she is there, the girls do what she wants - she is one of the best speakers in the room (3 yr old kinder), super confident, very good at writing, language etc. She is a natural leader, and now they laugh because they say she talks all day!
The checklist I got last year was rubbish too - the things on there, checked off when she was 3.5 were things I knew she'd been doing since she was 2! Don't worry about the checklist - it sounds like your little one is developing just fine, maybe is just shy or a quieter child.