First, for reference, some general support pages:
Use Google Apps and Services Built Into Your Car
Use Google Maps features for your electric vehicle
I do not have access to the vehicle right now so I did some testing on Google Maps for Mobile. I did not realize that there are options in GMM to set your vehicle plug types. (Settings -> Electric Vehicle Settings)
First suggestion: If there is a setting in Google Maps for Android Automotive then remove the J1772 option from Google Maps.
Based on my past use (not recent unfortunately) of the Google Maps API, I suspect there isn't a setting for a search radius. Google is likely to show you a fixed number of the nearest points based on some magic algorithm occurring on the server. Typically if you switch to list view in Google Maps products there is an option to load more at the bottom.
Second suggestion: Try to get more results by switching to a list view (if available) and scrolling to the bottom. Return to map view or, ask Google Assistant to load more results.
Google Maps for Web has a setting for the number of results to return for each search (this is more aligned to the API.) It also has a setting to increase that number with a warning that it will take longer to return results.
Third suggestion: See if Google Maps for Android Automotive has a similar setting or see if the setting in Google Maps for Web carries over to the vehicle to get more results the first time.
Personally I prefer
suggestion one if it is available. Returning fewer results that are more relevant is why I give Google access to my personal information. I might try variations on this solution, for example trying to ask Google Assistant for "fast charging" or "ccs charging".
As I don't get to drive our XC40

I can't do this testing myself. I'm hopeful that if someone on the forum can't provide an authoritative solution someone can do some testing and give us the results.