I don't believe an Imprint is the same as a record company. I believe Westbury Road is a distributing imprint of Roc Nation while Parkwood Entertainment is a production/management company in association with Columbia records. I guess this is a standalone label like Interscope for example. Congrats nonetheless
What Beyonce has is an entertainment company, not a label. And no, Janet isn't the first black woman to start their own label. Janelle Monae just started her own earlier this year. I think they said arguably is because unlike Janelle, Janet was a major artist on major labels her whole career and has now transitioned to her own label. Pretty much no black female of her stature has done this. Either way, it's great that another black woman has their own! Hopefully other black females in the industry follows suit.