US did the same, Southern California was 50 Hz at first. It didn't convert until after WWII
https://www.lifebynumbers.ca/history/the-rise-and-fall-of-25...
Sir Adam Beck #1 ten 25 Hz generating units were converted
to 60 Hz or modified as follows:
Units 9 and 10 to 60 Hz in 1956
Unit 3 to 60 Hz in 1970
Unit 4 to 60 Hz in 1984
Unit 5 to 60 Hz in 1985
Unit 8 to 60 Hz in 1990
Unit 6 to 60 Hz in 1996
Unit 7 to 60 Hz in 2009
2009! Talk about legacy support.* https://en.wikipedia.org/wiki/Sir_Adam_Beck_Hydroelectric_Ge...
* https://www.opg.com/stories/opgs-sir-adam-beck-i-hydro-stati...
universal motors in particular do not care at all about frequency