Yup. Just like any other battle. If you win, she's your prize to do with as you see fit.
It might make sense to take it as Tonnage if you're Motive rewards sinking Warships. Or as you point out, to add to your "Scouring the Seas" bonus. Or just because you don't intend to take any more Refit actions because it is late in the game or there are no attractive Upgrades.
Thanks!! A quick follow-up: Is the Bold Attack preferred when you try to sink some merchant ships in the same ocean? I try to only use stalk, but that seems to be too slow ... (more of a strategy question ...)