Agreed but the "one breaking a circle" stand by symbol, IEC 60417-5009, is what the article seemed to be referring to by "one inside a circle", given the pictures shown. I just copied their imprecise description.
I'm glad you clarified. The symbol has always represented an open 'O' vs closed '|' circuit to me (never bothering to look at the standards). The fully inside vs breaking is still fitting in that context.
