Out of interest – I notice you missed the word Boiled from your patch testing of linseed oil…
NOTE: this isn’t just linseed oil, but a mix of linseed oil with solvents and other goodies that makes it go off like varnish (and also spontaneously combust)…
If you just wiped plain linseed oil on, I’m not surprised it wasn’t very effective!
Disclaimer: never used it as a metal protector, but have for gunstocks.