No
It's because "it's a BBC scandal" when what happened was BEFORE she was employed by them, when the BBC found out they acted.
It's amazing how many "BBC scandals" involve stuff that happened outside of work, in the persons private life, or before they were employed by the BBC, and in some cases decades previously or whilst they were working at another broadcaster.
IIRC the BBC (and a lot of other companies) started to tighten up and check more of of potential employees social media stuff a few years, but given those tweets were from 7 years before the BBC employed her, how far back and how many of a potential employees social media accounts do you expect them to check? (and then we get into the "scandal" about the "BBC cancelling staff over private comments" and "wasting tax payer money on pointless checks" and "BBC invades staff privacy").