Yes, I am sure they are removed by Picard on some occasions.
I ran into this issue when using Picard Plugin: Format Performer Tags
When I used a script that achieved something similar, trailing spaces were respected.
But when using the plugin, trailing spaces are removed.
The plugin creator ( @rdswift ) had a look at this, but confirmed it must be something that Picard is doing.
It’s not a biggie, and there might be valid reasons for this behaviour, but personally I would be in favor of removing that mechanism. (not the spaces)