"Breakneck speed" and "building spree" relative to what? To Terra at the height of the Star League? To Luthien in the First Succession War? Hesperus II at its 50s-70s height? Or, perhaps, relative to the decades immediately preceding 3145?
Well, if the text section—or the whole book for that matter—is set in relation to the period prior to the Blackout—or more specifically in relation to the period before the FORTRESS—I'd say the building spree is relative to that time frame.
I get why you'd want to split hairs, or why some players need to know every ship component down to the last rivet, but it's not really necessary for a good story or good universe building. If this is about comparing eras, then FORTRESS production is less than in the SL, but more than during the SWs. But honestly, that's irrelevant within the timeframe. In this regard, Republic aerospace industries have seen noticeable growth in production. Since we also "know" the RAF has expanded it's front line forces to roughly 20 regiments from 5-6 during the period of the Fortress—and sustained losses in the process—we can reliably infer that text stating BattleMech factories have also increased production is also "true."
As Weirdo once said, "...if you want to keep changing the goal posts just let me know." Overall front-line ’Mech forces are known, but outside of a few notable exceptions the total number of DropShips & JumpShips is never stated. Nor are their relative production numbers statted—at least not for some time. Part of this is to avoid mistakes made by FASA, but also so people can use what they need for their own games.
Given enough time the setting will change to a new status quo, and at that point we'd need new explanations, but I think these make an okay first set and could last for an Era or so.
Absolutely spot on. And while we're progressing through this era into the next we'll tackle the gameplay-related questions necessary to determine whether or not WarShips make a comeback in the next one. Hopefully, through a combination of something like: setting changes, tech and rules changes/modifications we'll find a way to keep WarShips in the setting.