A pound difference is enormous.
Weight will vary from a bike to another as a result of manufacturing discrepancies in framesets and parts/components, but 1 pound is a lot. I mean, people will pay 5000$ more for a bike just to shave 1 pound out of the total weight.
The advertised weight for most manufacturers is for 56cm framesets so you're right saying that your 50cm should weigh less. For instance, my 2024 SL8 Pro in size 58cm came up at 7.3kg on the LBS' park tool scale. Its advertised weight is 7.16kg (size 56cm). I don't mind the 140g difference given that it's a size bigger.
Are you 100% sure that your scale is accurate? Have you tested it with other items to which you know the exact weight?
Last edited by eduskator; 04-29-24 at 05:10 AM.