How accurate are portable luggage scales compared to airport scales?

Across r/travel and r/onebag threads we read, owners of mainstream 110 lb handheld scales typically report agreement with airline check-in scales within roughly 0.5 lb to 0.5 kg, which is well inside any airline's tolerance for the 50 lb / 23 kg limit. Repeatability (weighing the same bag twice and getting the same number) is generally cited as the bigger real-world tell than absolute accuracy.