The refit and recommissioning of the Discovery as Discovery-A on Star Trek: Discovery is a break with Star Trek canon. 1 / 7
The Enterprise wasn't recommissioned after its own refit in Star Trek: The Motion Picture... 2 / 7
With its identical successor ship being recommissioned as the Enterprise-A in The Voyage because it was exactly that. 3 / 7
The USS Defiant also wasn't renamed the Defiant-A after its own recommissioning... 4 / 7
While the Discovery is still called that in 'Short Trek: Calypso', set a thousand years after season 3 of Star Trek: Discovery. 5 / 7
However, Discovery was in its second season when Calypso was being produced, so this may not have been foreseeable... 6 / 7
And the Discovery-A may have been decommissioned to the Discovery, or Calypso could be non-canon. 7 / 7