Irrelevant questions I know, but...
How many accidents or incidents would have been avoided if W&B calculations had been done on an approved piece of paper rather than an unapproved electronic system?
If a pilot is willing to take the risk that W&B calculations done by an electronic system are not accurate, why would that same pilot bother to do accurate calculations using the approved paper system?
My experience is that it's pretty simple to confirm that calculations done by an EFB W&B system 'match' those done using the approved paper system, at the various extremes of the envelope. And on the paper system a pencil thickness can 'weigh' kilograms and accumulate to an inch of difference anyway...