Just got an email from this supplier and I’ve noticed that some of the rifle ammo like this 5.56 they are selling has a strange look around the neck of the cartridge. Almost looks like it was blow-torched or something?

What is that exactly?

Looks like mine does when I anneal it.

Flash has it right. Have some new 5.56 Lake City brass that looks just like that.

Nothing new or strange.
The burnt look is from the annealing process. Annealing softens the brass and removes the stress from being shaped. The brass would be too brittle from work hardening without being annealed. To anneal you heat up the metal and let it cool slow.

Yes, discoloration from the annealing process.

Military type ammunition usually looks like that because the manufacturers don’t need to polish off the discoloration as they do for ammunition generally sold to civilian consumers to make it look pretty.

7.62x51mm also from the SG Ammo site:

You're all giving the OP a false sense of security. That ammo is garbage and downright dangerous. I've emailed him my address for shipment to me for safe and proper disposal. Even covering shipping to ensure I get that dangerous product out of his hands...