Here is a copy of the German datasheet.
ASCO-Preciflow-R-202.pdf (276.6 KB)
It states: “Variabler Durchfluss proportional zum Magnetstrom” which translates to: “Flowrate proportional to current“
The resistance of the coil changes significantly with temperature. With constant voltage, the flowrate will change with coil temperature. Only you know, if this will cause issues in your application.