I agree with The Economist (covid). It has to do with the frequency of use. Similar to radar and laser, covid has become an everyday word. It is also a combination of not only first letters but a mixture of 'first and second letter' and 'first letter' only. It does not have to follow the rules for SARS (which is an inititalism: first letters only).
“You gotta be proud of yourself!” is an invitation to the listener to share their feelings.
The appropriate response depends on the emotional states of the participants in the conversation, and where the responder wants to go with these.
There is mirroring as a step to deeper sharing:
“Probably the way you did when you nailed the Miller case.”
There is ...
What is the short answer for response to “You gotta be proud of yourself!”
“have” is sort of hidden by the colloquial “gotta/got to”
It is not: gotta be = must be.
Thus the replies: "Yes I am" or "Yes, I was" are correct.