Reproduction steps:
1. Create a new HDRP Template project
2. Create empty GameObject and attach a Light Component to it
3. Change Light Intensity unit of measurement to EV 100
4. Change Light Type from Point to Spot

Expected result: Intensity value will be converted from EV 100 to Lumen since the unit of measurement was changed to Lumen automatically
Actual result: unit of measurement gets changed from EV 100 to Lumen but Intensity value stays the same

Reproducible with: HDRP 0.1.21 (2018.4.1f1), HDRP 4.10.0 (2018.4.13f1), HDRP 6.9.2 (2019.2.13f1), HDRP 7.1.5 (2019.3.0b12, 2020.1.0a14)

Note: this works when changing Light Type not only from Point to Spot but also many other variations (Point -> Directional, Area -> Spot, etc.) but you need to choose a unit of measurement for Intensity that is not the default for the Type you are changing to