The A440 vs A444 is something I actually understood. Musical notes are like minutes on a clock. People invented the method to measure time as they invented the method to measure music. Although my clock switches to a new minute when 60 seconds pass, if I decide to set my clock 10 seconds faster than yours, it still accurately measures minutes, but the minutes will begin and end in different places. The intervals will be the same, but everything will be 10 seconds ahead.

I don't know if folks with perfect pitch can hear a difference as slight as 4 Hz, but you could drive them crazy with scales based on A(not)440.