An 800 number and a po box ?
They could be a legit business veture. . but . .
I’ll wager that they’re just a clearing house and they own no inventory.
Only after you place an order ( they claim to have everything ) do they begin to source the part and drop ship to you.
And maybe that’s good enough for you . .
IF . . one stop shopping is what you’re after and you’d just as well have them do the footwork to source the part.