The whole point of this message is to say Warning: if you block this certificate tomorrow, you are going to break other things
When creating bootable media or modifying a distribution point you will get this error if you use the same exportable certificate more than once. The cert is used for management point contact when it hasn't been issued a cert.
The error can safely be ignored unless you want to create some media that you only want active for a short amount of time, then you should use a newly exported certificate. This will enable you to be able to block the cert in the console.
