Nursery teacher here. My current school has an optional uniform for the nursery of joggers, blue polo shirt and sweatshirt with school logo on. Lots of parents do send their children in uniform or part of it, but a fair few don't. I don't tend to notice much either way except the odd tut when a child comes in in something clearly expensive and unsuitable (I work in a naice school with children whose wardrobes are probably worth as much as my car) for the day the child is going to have.
Last school the 'uniform' wasn't optional, but it amounted to a polo shirt, dark trousers, skirt or dress (or shorts in summer) plus a red jumper or cardigan - could be the school logo one but could also been the plain supermarket ones. That applied to reception too, then the more formal uniform from Y1 upwards. Lots of parents there chose to send nursery /reception children in the more 'proper' uniform either because they just thought it looked cute or because it was passed down from older siblings.
To be honest, I'd be worried the school didn't have a good early years ethos and that the setting might be more formal than I would like. Nursery children should have free access to the outdoors - in all weathers, they should be exploring and experimenting with paint, chalk, sand, water, dough, mud, flour etc etc. They need clothing that's fit for purpose. And more importantly should be developing independence in helping to get themselves dressed and undressed, toileting, changing for PE if that happens, or for things like dressing up in the role play corner. A full on shirt and tie uniform is not supporting them in that - too many fiddly buttons.