The asset picker for EditContext reflection of AssetId is bugged. The field is not filled out after selecting the asset from the browser.
The workaround is to start typing after several letters the asset will be shown in the list. Picking from the list works as expected.
I am putting the issue here but this is not specific to CsvSpawner - this happens on other components serializing AssetId as well.
This is the o3de bug.