If I am not mistaken this is dependent on 1) how you purchased your ticket, and/or 2) how secure your credit card is.
For 1), if you purchased it through an agent, SQ
should not ask for your credit card as you are not paying SQ directly. It is the agent's responsibility to ensure that they can collect payment from you, not SQ's.
For 2), this is for situations where you have purchased a ticket directly from SQ's website. If your credit card does not have added authorization such as the 2FA (two-factor authentication) where the credit card company/bank sends you a text with a code or you use a token to key in a code during payment, then SQ may request for the physical card.
As an example, I recently purchased my SQ tickets via expedia which did not require the 2FA. However, I had absolutely no problems checking in or traveling because expedia was confident that it was able to collect my money. On the other hand, I had also booked directly from SQ's website and had to go through the 2FA process, which was sufficient enough not to require a credit card check at check-in.
Hope this helps but please don't quote me!
