Forget Learned Objects does not forget the names assigned.
If one erases LEARNED data for an algorithm, the obj ID's get erased, but the earlier associated names do not get erased.
Subsequently, when one trains / learns a new object id, it gets assigned the previous name that was used for that ID#.
The only time all data is forgotten is if one does a Factory Reset.
That is very drastic, as it erases all data, not just the ones in a specific algorithm.