In which direction? Height, Width(dia), Length? I agree a millimeter in lug-2-lug (length) can make/break a watch for smaller wrists. I would also say a few grams in weight can make/break a watch as well. (Heavier "Heft" is NOT an indicator of quality)
I have small wrists 6.75" / 17.14 CM and could not wear the 39mm Omega Spectre cofortably-- but I can wear a 42mm NTTD Ti, Seadweller 43, Panerai 111..... Mostly because the Lug-2-Lug (Length) is short enough for the wrap.
Take modern Tudor, their slab side cases and thick movements ruined the Black Bay 54 ... a 37mm watch. Unbalanced on the wrist.
Final example: Seiko SKX, Turtle & Willards with a published diameter of 42 / 44 / 45mm! They wear smaller than a 40mm modern Submariner. Anyone can wear a 42mm Seiko SKX...
I had a buddy who worked at a major US watch retailer, and most watch retailers are secretly "rolling their eyes" at customers who claim I can't wear anything larger than X or I only wear X diameter watches.