Hi @Cobion
In the context of an SPN you can only have one SPN entry per forest, i.e. host/server1 can only exist on one object. The setSPN command has logic to check if an entry exists before it's added. If you do try to bypass setSPN and set the SPN directly on an object using a AD editing tool, such as ADSIEdit, LDP, etc this will also fail as the DS service also prevents multiple entries being created.
The linked post is talking about changing the permissions and who can change the SPN value, this doesn't change the underlying logic which will prevent multiple SPN being created.
Gary.