wrote

When I go out, I see lots of people wearing masks.
I also see medical people wearing masks when
dealing with COVID-19 cases. Why is this?

In the case of the general public, they dont understand
that the only real benefit of that type of simple mask is
that it makes it harder to touch your mouth or nose
with a finger which is contaminated with the virus.

In the case of the medical people, those with the most
clue use much better than simple surgical masks which
have a completely different purpose, stopping some of
the germs from the medical person infecting the patient.

The BBC was unequivocal, at the start of this crisis, in stating that
masks are not useful as a preventive measure against COVID-19.

They didnt say it as absolutely as that.

Was the BBC wrong,

No.

or lying?

No.

I don't recall seeing/hearing any official
retraction of the previously stated position.

Because what they said is still correct.