I have had a few AMEX over the years, even during the depths of Covid when I was on a casual income. Very easy application and approval.
Westpac told me they do not approve CC's unless on a full time income(their words at the time).
I have been back at my full time job for 18 months and swiftly rejected for AMEX around six months ago and then again just recently. Before any proof of income was asked for, or was I given a chance to upload any.
I rang both times and both times they mumbled something about a letter in the post and could not give a specific reason, blah blah.
I have learnt not to be too upset by these things and thence applied for the V Flyer-citi card and was approved fairly straight forwardly...
Who really knows how these things work. The whole job has become a bit more challenging, just adds to the fun of it i suppose..