Not a big issue, but there's currently no way to use the "Default" view mode to render an entity when using the LeafletMap view style. The closest it gives you is the full content display which holds special meaning, as that's ideally used for when the entity is viewed on the frontend and can lead to effects such as this where certain special fields may be rendered when they shouldn't.
Under a leaflet map view. Set the leaflet popup source to Entity, and switch the Popup Source to "< node entity >". "Default" should be available as a view mode option, but isn't currently available.
Use the entity display repository to get the view mode options so that it works just like core currently does, without needing to manually build the options.
Provide issue fork / merge request.
The "Default" option will now be available to select.
Fixed
10.2
Code
Thanks for this heads-up. Patch provided accomplishing what is being requested ...
Patch #2 committed into 10.2.x dev branch, will be part of the next Leaflet module release.
Automatically closed - issue fixed for 2 weeks with no activity.