It does not follow AABC, but instead it depends on the round number and the amount of conduits you managed to defend that round.

Excerpt from the page on disruptions missions, where you can find a table explaining the rates:

"Disruption does not follow the traditional 'AABC' rotation for endless missions. The reward tier is determined by both round progression and round performance, i.e. the number of conduits successfully defended."

For as it applies to gauss prime relics, pools A and B can be reliably found by only defending up to 2 conduits each round. So, as long as you dont protect 3 or even 4 per round you can consistently pull from the right pools

Although Axi B7 can still be found in pool C, so really it doesnt matter how many conduits you protect