Yes Drew, I went through the Imperial/Metric hoops in the late 50's early 60's. All the more confusing for some here because Europe was using the MKS system when we all changed to the SI metric.
The errors encountered with different drawings using the CM as base and others using MM were not always obvious. More than one Trinket box was made big enough to house the tool collection.
All but a couple of my latest measuring devices are dual Imperial/Metric and I still use either dependant upon whichever the old brain accepts as a visualisation.
Biggest problem I had whilst still working in the aircraft industry was that materials, tubes, sheet metals did not change in manufacture, just the SAE specs adjusted to accommodate variations. Inevitability being that a lot of things did not fit.
We still suffer from retailers quoting inaccurate dimensions.
1/4" is regularly quoted as the same as 6mm, when it should be 6.35mm
1" quoted as you yourself referenced as 25mm when it should be 25.4mm.
In timber joists etc. not relevant as it's well within the expected machining tolerances but is a real pain when it comes to machinery and tools.
How many Turners have fallen foul of the repeated listing of tool shanks by the retailers as being 5/8"-16 mm and then found that they won't fit in their existing tool handles.