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Quite often the labelling refers to the main triangle only.
I've seem mountain bikes labelled reynolds 853 but massively heavy because they've used shit rear stays. This is usually because they want to shape them, thin wall are harder to shape and big manufacturer can't be asked.
wildwest-
The main triangle part is true - generally x3 main tubes to get the sticker is the requirement. That said, chainstays/seatstays aren't going to make a whole lot of difference to the overall weight as they're such a small diameter it's going to have a negligible effect on overall frame weight whether they're 0.9 PG or 0.8-0.6 DB. I think this is essentially why x3 main tubes for the sticker came about - there's not a really a whole lot of sense in opting for posh stays. I'm sure some will say DB/thinner stays ride better though.
Alb
Apologies. It was a grant rant 10/10. You realise Reynolds 520 is just bog standard DB 4130 Chromoly with a sticker, right? Smoke and mirrors, Columbus Cromor, Tange Champion, etc, etc...
As for when steel frame got heavy and dead riding, well, you can thank the emergence EN/ISO standards and testing for that - compliant frames are massively overbuilt.