spoilers:end of spoilers
Well, Legendary has to license Toho monsters on a case by case bases. As a matter of fact, although this film always intended to use Mothra, they weren't sure they'd be able to use her, so the earliest cuts of the movie had an original placeholder monster until Mothra was cleared. A credit about Godzilla and Mothra being owned by Toho is one of the first prominent end credits.
Which is to say: if it was officially Manda then it would be listed as such! So, no. It wouldn't be the first time Legendary produced an off-brand version of a Toho creature, though. A skeleton resembling but somewhat different to Anguirus was seen in Godzilla lair in King of the Monsters.