The reason it's a disingenuous argument is that the H-1B is not technically transferred: The new employer is actually filing a new H-1B petition, which, yes, is not subject to the lottery. And the employee can start working while the petition is pending.

But here's the thing: Even though the new petition is very likely to approved, it's not automatically approved and there's no guarantee that it will be. Particularly if the new job doesn't use the skills that make the employee special.

It also adds uncertainty to the job hunting process. And, if the current employer finds out that they're looking, they could be fired... which technically makes the ex-employee immediately eligible for deportation... which means there's no counter-offers.