Between Ost-Brg-Gent there are no feasible alternative routings. In fact this whole line was opened shortly before WW2 as a all-new direct line (look at a real map) to relieve the old meandering lines serving many more settlements. That is still the case between Gent-BRU, the ´new´ĺine is nonstop direct but some trains will divert and serve Denderleeuw (about halfway, just south of it, junction for the Kortrijk line). The oldline is 50 (all Belgian raillines have a nmbr that is also used in old timetables, laws, leaflets etc, even in most newsppr news) and the new one became 50A. The old line runs via Wetteren (junction for direct to Mechelen)-Aalst (fairly big town)-crosses the new line-Denderleeuw-then over the line again and via Bru suburbia to Brussel north via Laken, whereas the nw line runs into BRU-south. Your rerouting must have used this or one half of it.
The old line Brugge-Gent ran via Eeklo, but Brg-Eeklo is now bus, or museumtrain/weekends part of it. From Eeklo hourly only weekdays (or at least that was so). De flemish bus deLIJN runs an hourly bus along that line from Brugge to Gent (which is also an oldtime song of Jacques Brel) in 1h30m or 1,40 for its standard fare of 3 eur (1,60 on a prepurchased LIJNkaart).
The max speed is in line with about the whole of the normal BE network. The only HS are those used by Eur* and Thalys and from Antwerpen to NL also by the BeNeLux trains. Perhaps there were special speed restrictions in force due to those works.
A side note: this was also about the first stretch of Belgian Motorway to be built, also before ww2 it hink and had on very busy sunseekerdays even ONE way on both sides-to sea mornings, to city late evenings! Those wanting the other way had to use the old side roads!