Please don't cross-post.
As far as I know, the information in this thread is still accurate. The updates occur once a year. You won't see changes from a few days ago until next year sometime.
However, if you want a definitive answer, you'll have to call tech support. Things change over time. Garmin uses OSM maps in other devices. But that does not mean they will continue to update them for legacy devices like the Explorer+. That unit uses maps in the original DeLorme format, not in the standard Garmin format. So extra work is involved.