I thought @JoeRockhead had a good breakdown, @MikeyMagic. Not sure if this is an "insider" and if he is, he didn't really reveal very much that isn't common knowledge. And some information appears false.
For one example, I've observed with Chase (and other major lenders) that they seem to have starting limit ranges that vary based on the card profile. There are the starter cards like Rise that are oriented towards thin or damaged profiles and have lower limits. Also, the basic low-APR Visa/MCs tend to have lower limits from my experience. Next would be the no-AF rewards cards. Then the lower-AF rewards cards ($95 to $150). At the high end would be the high-AF premium travel cards. I was 0/24 with Chase and was approved for five cards over about 18 months. And my approvals for various types of cards followed that model, even though nothing else significant changed on my credit profile. And the lowest approval wasn't the last. So, IMO, the specific card matters when it comes to SL. Now, what the posting said about the tiers may be correct in that certain metrics must be met to approve at the top end of the card range. Lenders seem more willing to bestow larger SLs on high AF premium travel cards.
Just a note, @MikeyMagic, if you're going to copy/paste from elsewhere on the web you really need to provide a link to the original source.
If someone on Reddit did a copy/paste from one of my posts on here I'd be very unhappy if I wasn't cited and linked. 