Yeah, that drives me grazy. If I look into W3/SVG (
https://www.w3.org/TR/SVG/coords.html) "7.10 Units" it starts with:
All coordinates and lengths in SVG can be specified with or without a unit identifier.
If I remember correct, there were some SVG teacher's who recommend to initialize the coordinate system with a first measurement unit statement like you have explain to me.
Well, that's life. Have a nice week end.
DD