That’s no longer the case (at least in the UK): In the early days of contactless the device would indeed skip authorisation (which is why contactless used to be almost instant). Nowadays the authorisation is usually performed “live” for contactless transactions (you may notice that you usually need to wait a few seconds after tapping the card against the reader while the device communicates with the issuer.)
The reason why PIN+contactless is uncommon in the UK is because in the UK the PIN is usually verified locally with the card: The PIN is stored on the chip, and the PIN is verified before the terminal even communicates with the network. In a contactless transaction, however, you can’t do that, as the chip is unavailable.
In some countries, the PIN isn’t verified locally against the chip, but online against the bank. I believe most German cards for example don’t have the PIN stored on the card at all (at least that’s what the banks used to tell us). In that model you can do PIN+contactless again, as you have to communicate with the bank anyway for PIN verification.