This article will not be answering the question posed in the title.
It tells you about one weird case of a friend who got the HDFC Diners Club Black (DCB) credit card as First Year Free (FYF) at the lowest ITR that I know of.
You may make up your mind about the posed question yourself.

I have tried multiple times to apply for HDFC DCB. HDFC rejected the request each time. If you are one of the lucky ones to get your hands on HDFC DCB in its hayday, I am envious of you.
This is one case which makes no sense to me as to who HDFC deems as worthy.
This is a small story of a friend's wife who got her hands on HDFC DCB.
Just two years prior she did not even have a credit score. That was pre marriage to a Cardgyani (lets call him X).
X tried applying for a credit card for his spouse even before applying for a "Marriage certificate” (ouch).
However, all her applications were rejected on account of nil credit score. IDFC first, SBI, Axis Flipkart and even Axis My Zone all declined her request for a credit card.
They tried for HDFC and she was approved for HDFC Millennia with a limit of ₹80,000 on condition of opening joint savings account in HDFC.
Few months later out of the blue, she got a limit enhancement offer to ₹10 lacs.
Facts: her monthly spends were less than ₹10,000.
All Cardgyanis know, that ₹10 lacs credit limit is the golden line beyond which you become eligible for DCB or Infinia credit card.
And she applied for HDFC Infinia, but was rejected.
One month later, the offer for FYF DCB was given by the bank which they promptly accepted.
Some more facts, X has an ITR of < ₹25 lacs while his wife has ITR < ₹13 Lacs.
I can't count how many times I have seen X fill the form for an upgrade to DCB. No surprise, that it was always rejected!
Then he tried changing his strategy and attempted to increase his limit first. HDFC humoured him by giving a limit increase if just ₹10,000.
Maybe what prompted, the limit increase was that they had taken a joint home loan from HDFC (a high number with 6 zeros) which also got them the HDFC preferred savings account. Maybe that is the trick.
Recently, he also got an add-on DCB card for himself which he is brandishing about. Last I saw him, he was busy calculating how many Amazon vouchers he should buy via smartbuy.
Conclusion: If the credit card companies have figured you out for a Cardgyani and won't upgrade your cards. Just get a spouse and try again!
This conclusion maybe is the reason X is called X here.