In most industries contractors actively avoid "discovering" anything of historic value.
In construction for example, if you uncovered an amazing archaeologically significant site, it will be a huge pain in the butt and cost everyone a loads of money due to delays et cetera.
In the case of a shipwreck, it's not going to be heavily laden with gold bullion you get to keep. It will merely be "interesting" in "enhancing our understanding of 1700s naval operations" or some such. You probably won't even get credited with the discovery.
The ships equipped for industrial operations at sea like this cost an absolute fortune to operate. They also have contracts lined up months or years into the future. These contracts have crazy financial penalties for delays et cetera. This means any kind of delay in fulfilling a contract can be disasterous.
Additionally, I don't think much detailed survey work would be done prior to laying cable because that would be preclusively expensive. They would check depth per existing charts, maybe check what the sea floor is composed of geologically speaking. They definitely aren't sending down remote controlled rovers to check for ship wrecks.
Honestly, I reckon they just steer the boat and spool the cable off the back, pausing momentarily to splice in the next cable when necessary.
If there was a big flashing sign that said "super interesting ship wreck right here" they'd close their eyes and make sure no one on board noticed that.