The OP is correct in that actual usage of "biweekly" is ambiguous. The "bi-" prefix, meaning two, might mean every two weeks. It also might be two times per week. I know I've seen it used both ways.
Both senses even make it into the dictionary definitions, frex:
https://www.merriam-webster.com/dictionary/biweekly
If you really want to be unambiguous, semi-weekly is good, but you'll have to pair it with "fortnightly", which will earn you even more strange looks than using "biweekly" to mean "twice per week".
Historically, Traveller ship schedules revolved around a granularity of a week. A week to jump, a week to land/load/do business/load/return to jump point -- even though actually doing the math and rolling the variation in jump time might put you off a day or two here or there. So the "every two weeks" sense is likely.
In this case, the context is also specifically that for the Maintenance Disas (B143). In the description for that Disad, twice per week isn't a Maintenance frequency (though every other day is), and "Bi-weekly" appears in the maintenance interval chart between "weekly" and "monthly".