Why are the QMac and QWin F/X Rates (Slightly) Different?

I am a long time QWin user - dating backing to 1995 - but am considering moving to QMac.

I spent part of the weekend setting up QMac to run in parallel with QWin until I decide whether to not QMac will meet my needs (note: here is to hoping so as the though of QWin + Parallels + Windows ARM on M silicon is not appealing).

In order to make sure that I do not run into any problems I am comparing the Net Worth on QMac to QWin to make sure that everything is in sync.

In the process of further fine tuning QMac I noticed the following CAD / USD F/X rate between QMac and QWin are slightly different (but different enough such that the Net Worth amounts differ).

Would appreciate any insight into this as I would think they should / would be identical.