Another issue is with modern cassette ratio's and suspension designs, for which some seem not to consider the fact that mech cage lengths and operation with a growing chain line have not developed, rear mechs are still designed with fixed parameters in mind, suspension frames are not.
We did get mega range when large capacity sprockets appeared on cassettes, manufacturers clearly realised there that current cage length was an issue that a larger Jockey wheel could address.
But none of this seems to stop idiots like Commencal adding a Medium cage Sram to a bike with a gearing completely unsuitable, leaving large large and small small both unuseable while stopping the bike from attaining full travel from the third large sprocket upward when in the big ring.
Gear ratios and cage lengths are there for a reason, safe operation in any gear is what should be addressed with anything else just opinion. The fact is that stating you should not be in big and big is with regard to chain wear a fine opinion, but not actual operation, it is used by many as a bail out gear and by having the correct gear ratio/capacity it is safe to go in and out of it. If you cannot then in technical terms it is wrong spec.
Quite simply, if a customer went into the big ring from middle, while using the rear 34 low, if he lost control of the bike and crashed due to his rear mech hanger or chain bending or snapping the retailer would have a headache.
Try explaining to someone riding a full sus that his chain snapped because he should not have been in 44-28 when hitting a large bump?
Legally any bike that cannot safely operate in and out of all the gear ratios is not fit for purpose and probably should not have an EN sticker on it.
The second line in the picture Andy B posted states "must have" for a reason.
