Yes, I can see that for utility transformers, which are carefully optimized for the task.
But I would think that power supply transformers are likely to have larger margins so
they aren't operated so close to the limits.
paul
Here is a list of current production models of power transformers. Notice it has separate
models for 50/60 Hz and 60 Hz.
Many years ago, I bought an Epson PX-8 just prior to moving to Germany from the US. Using
a 220-110 transformer, it would take about 2 days to charge the battery, more than twice
as long as in the US. But the wall-wart transformer got very warm, much warmer than in
the US. Upon returning to the US with our 60 Hz power, all was well. The battery charged
fully in less than a day and the transformer only got slightly warm.
Just a data point.
Will