Again, the key problem with restarting Highlander production is that the tooling is buried under thousands of tons of radioactive rubble. Getting at it is possible, but would be both time-consuming and expensive.
We have the benefit of knowing that a lot of the production facilities are actually intact because they managed to stand production back up. In universe, they don’t know that. So playing around on Son Hoa is a big risk with a questionable reward.
On the other hand, once the new Longbow is in production, Szabó’s goal is to get the King Crab going again. He has the ruins of the line on Loburg, but he needs more info than he’s got there, which means a fishing expedition to Son Hoa to see if any part of that line survived. At which point, they learn that quite a lot of the facility there is salvageable. Not everything, by any means, but enough that they can fill in the gaps and get production restored, as in Canon.