Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines

Wouldn´t worry me in the least, been descaling Wilescos with ordinary household vinegar for many years, and never had any issues.
(Just flush it out with plenty of tap water, no need for destilled/demineralised, as it doesn´t form any limedeposits as long as you don´t steam it)

I suspect you´re spot on, and that they just want to sell more of their affordable "Z84 Decalcifying Agent" at $460/Gallon with MiniSteam

Sweet!....I NEED that $460/gallon funds for More cute little engines, thank you!