Most on this forum have seen these pics but just to show how different frame sizes can be made to fit.

Giant's use a compact frame that covers "Several" Frame sizes. I ride an "Extra Small" (XS) a Small and a medium. The XS frame fits from 46 to 51. The S fits from 49 to 54 and the medium I have no pics of in fitted form but is larger.

I reckon that my frame size is a 51 and the gold bike is that size. All these bikes fit me but the Black OCR did have to have a few parts changed to make it comfortable- But none of my bikes fit like the Gold bike- but that was a custom build on a race fit frame.
B3.jpg Giant OCR in XS size- Long seat post and longer high rise Bar stem

B1.jpg Giant TCR-C in S Size- Nothing changed except the saddle

B2.jpg Boreas Ignis in 51cm- All parts selected on initial Build.