YANBU.
I feel for you and your DC. I don't think this is okay. For small children, these rewards should be handed out on rotation, so that everyone gets it, making sure you catch the child doing something good.
I used to resent it when my DC tried really hard to do a project by themselves (because we were both busy, they had to make do without anything more than the odd bit of assistance), and every single time the reward went to the kids with the most involved parents.
One of my friend's kids told her mum at age 9 that there wasn't any point in trying because it was always the same kids who got the prizes. Perfection achieved through parental input was rewarded, not the kids' efforts.
I've learned loads since then though, and if this was happening today, I would share my thoughts with the school and ask them what they are teaching the kids with their reward choices. Coz from where I'm sitting it's nothing good.
If they must have stars of the week, then make every kid feel special at least once. A family member of mine is a primary school teacher and she talks about how hugely motivating praise from their teacher is to the children. So she always makes sure to find some kind words for every single pupil.
You might not want to say anything though, given your already stressful work and lockdown and all that, and that's completely fine, too. In which case, I would get a little star of the week sticker sheet so that you can hand these out to DS instead. Find a new category each week, or several permanent ones, give yourself and DH the occasional star, too, and maybe those teacher stars will not be so sorely missed anymore.