Weren't the House mech production figures written back when the idea that the Inner Sphere was still a "scavenger economy" still in effect and you were much more likely to obtain a new battlemech by defeating it on the battlefield and salvaging the remains than simply purchasing one?
Not really. Hesperus II "started out" as being the location of a giant warehouse full of functional battlemechs rather than the location of a factory where more are being built. Steiner was, IIRC, the first of the house books, and even by then Hesperus II was already a factory world. That being said, yes if you were shot out of your mech, you weren't likely to get a newly made factory built replacement. Being "Dispossessed" was, when all was right with BattleTech and lives were cheap but battlemechs weren't, the greatest fear of a MechWarrior. It was part of the lore that mechwarriors sometimes disabled their ejection seats because they'd literally rather die than live on after ejecting from their family's mech turned into a smoking crater.
Still, production numbers is an example where you can see an evolution in the House Book line. Namely, the first books didn't offer any. IIRC it's only the last two, Marik and Liao, that list them. Those numbers may, in light of the retcons that came about in the succeeding three decades, be viewed as incorrect information compiled by ComStar. Whether you choose it to be deliberate or not is part of the fun.