BUG: blank unchanged phone numbers triggering Task

related to:

I have this expression that is in the event and needs to be true to do a send email task:
[_THISROW_BEFORE].[Mobile Phone] <> [_THISROW_AFTER].[Mobile Phone]

The [Mobile Phone] column is of type “Phone”.

I had to hack it to be like this to work:
AND(
OR(
ISNOTBLANK([_THISROW_BEFORE].[Mobile Phone]),
ISNOTBLANK([_THISROW_AFTER].[Mobile Phone])
),
[_THISROW_BEFORE].[Mobile Phone] <> [_THISROW_AFTER].[Mobile Phone]
)

Why is this long standing known issue still present as a bug?
Should we really have to know to apply this workaround 2 years after the bug was initially reported!?

I wasted significant time drilling down to find this bug because there are so many things that could lead to it with my row editing actions.