The official MDA hardiness guide lists that species as zone 5. I'd also be wary because of BBB. I've seen plantings of non-native white bark birches like Dakota Pinnacle get hammered in the last couple of years.

In my region Betula nigra is following the established pattern of it being the main one the borer does not spoil. For example a friend had a problem with B. pendula 'Laciniata' branches and trunk sections falling onto his plantings because two of them were just over the fence in a neighbors yard. And got bored out, died and began breaking up in quite quick succession. As a river birch looked on with impunity, was left standing there by itself with not a sign of damage after the neighbor got the two 'Laciniata' cleared away.

I’m a sucker for lacy foliage, but red flags were popping up all over on this one. That’s not to say I’d never plant one…

Normally a body would expect a birch to produce catkins rather than flags

I thought the BBB wasn't as active in colder climates? And birches by their origins are cold-climate trees.

Anyway, maackia prb'ly wouldn't have been properly alarmed if he had been red-catkined.... :)