Allow me to clarify
It is not mandatory for you to clear your WASM folder each update as the sim should handle this for you normally however we are recommending users do so at the moment.
The WASM folder contains files that are generated by the sim on first launch of the A350 WASM.
These files then are cached for subsequent launches UNTIL either user clears them manually, or the aircraft is updated (so A350 WASM version changes)
It does not matter when you clear the WASM folder (before or after the update), as long as its done when the simulator is NOT running, on next launch the WASM Compile will be triggered.
Why do we recommend clearing WASM folder?
We have seen user reports where the sim has not handled this process gracefully, or their initial WASM Compile was somehow corrupted, so as a troubleshooting step we recommend clearing your WASM folder for the time being.
Thanks!