iPad Pro 2022 internet speed slower than iPad Pro 2020

A individual test result is, in isolation, not necessarily an accurate indication. You are potentially comparing Apples and Oranges - as your two iPads, running fundamentally different versions of iPadOS, may be routing traffic via different external gateway services (e.g. Apple Private Relay).

As is, you are comparing substantially different system hardware (M2 SoC vs A12Z CPU) and different Operating Systems (iPadOS 14.x vs iPadOS 16.x).

As for your iPad Pro6, perhaps the best that you can hope achieve in comparing network performance of you two iPads Pro is to ensure that you have fully disabled Apple Private Relay.

As all models of iPad Pro are capable of update to iPadOS 16.4.1(a), a more accurate comparison can be made by updating both of your iPad Pro devices to the most recent version - in addition to which iPadOS 16.4.1(a) includes essential system security updates.