The mandatory trigger at 5,000 encounters/day (or 8,500 single-day) implied acceptance of very high volumes—potentially ~1.8+ million encounters/year—before full expulsion authority kicked in. That expulsion authority only lasted for 3 years. It also codified/expanded release authority for asylum seekers under certain "operational" conditions.

The main point is that Biden acted like his hands were tied and Trump showed that they clearly weren't, and that we already had the tools to effectively shut down illegal immigration (through the border, at least).