Recently, while using the Go To XY tool in ArcGIS Pro 2.6.1, I stupidly entered a UTM coordinate as 6885000 3819700 with space delimiter, forgetting to enter the UTM Zone.
When it didn't work, I contacted Esri Tech Support because I thought it was a bug. After a week of testing, and several emails, Esri told me that I forgot to enter the UTM zone. Once I did that, it worked fine.
I'd like to suggest explicitly breaking up the entry for a UTM coordinate to include the zone, and also avoid potential delimiter issues.