Could be - but why so far out of the city?
There are six indexed births of Roberts with mother's maiden surname (mmn) Archibald, all in the city of Aberdeen, the last one being Mary Ann in 1900.
1901 census has John Roberts, 49; Mary, 42; John, 18; Bella, 16; James, 8; Frank, 6; Mary A, 1. I note that Francis' mother's surname is not listed in his entry in the births index, so I checked and it looks as if 1894 is one of the years when the mmn has yet to be indexed.
So I checked again in the index for births in 1918-1919, and there are three female births of Sh*r*f* with no mmn in or very near Aberdeen City:
Helen, 1918, St Nicholas, no 78
Ann Omond, 1919, Woodside, no 10
Elizabeth M Agn, 1919, Dyce, no 26
BTW St Giles Registration District is in Edinburgh.
If Stanley's daughter was aged 1 year and 8 months on 30 June 1921, she would have been born around October 1919.
Now, births are numbered in order of registration, starting with no 1 at the beginning of January each year.
There were 1220 births registered in St Nicholas in 1918. That's an average of 102 per month, so Helen would have been born in about January 1918. Her birth is also registered as Helen Cow, which means she was the illegitimate daughter of someone named Shirreffs and someone name Cow. I'd have to pay for the certificate to know which was her father and which her mother, but as she is obviously not the daughter of Mary Ann Roberts it's not worth it.
By similar logic both Elizabeth M Agn would have been born in about October 1919, and Ann Omond in January 1919. I took a look at Elizabeth's birth certificate and it's not her.
Mary Ann Sheriffs who was born in Udny is no 18 of 33 births registered in Udny in 1919, so she was probably born about July 1919.
Mary A R Sherriffs, 21, is in the 1921 census in Aberdeen St Machar, but she's not your Mary Ann Roberts because in the same household are Peter, 26 and John S R, 0. This child is John Skea Rendall Shirreffs, born 1920, mmn not in index. Peter Shirreffs married Mary Ann Rendall in 1919.
So I am still stumped to know who Stanley's daughter was. I may have missed something, of course.