Grid onEditCell event set to false but still triggers DataProcessor

I’m working on an old application where I have a grid with an onCellEdit event and dataprocessor attached.

At onCellEdit stage 2 I perform a validation.
If the cell input is valid, I return true from onCellEdit, the dataprocessor triggers and the database is updated.
If the cell input is not valid, I return false from onCellEdit. However, the dataprocessor is still triggered.

It seems I misunderstand what returning false is actually doing - it has no influence on the whether the dataprocessor is triggered.

How/where do I temporarily disable the dataprocessor from triggering, if the cell value is invalid, and then re-enable?
Also, if the cell value is invalid, I want to reset it back to its old value. It appears that this going to trigger the dataprocessor as well.

Please, try to use the grid validation:
https://docs.dhtmlx.com/grid__validation.html