Doubt from Hybridization

The hybridisation of ClO2 is sp2 it has 2 sigma bonds, 2 π bonds, 1 lone pair and 1 single electron.
The hybridisation of NO2 is also Sp2 it has 2 sigma bonds, 2 π bonds and 1 electron.
Why do we not consider the single electron in hybridised orbital in ClO2 whereas we do it for NO2?

I think this can be the reason that NO2 forms diamer , whereas ClO2 does not