That is correct and we’re working on better plots that are valid for discrete outcomes. Meanwhile you can use the randomized approach described in Predictive Model Assessment for Count Data to make valid plots. The randomized approach is not optimal as it adds randomness, but it is valid.
I was going to recommend plots for discrete outcomes, but then you already mentioned that they look good. As you have (1|id) terms it is possible that your model is overfitting (seeing loo diagnostics would help) and PPC don’t reveal problems, and thus LOO based diagnostics would be useful, too.