It sort-of auto switches to max for me if the cabin temp is really hot. But the cabin temp sensor data is not accessible without a Tech II tool. You might have an issue with that sensor in the B-pillar next to the driver's left ear. You might pull the pillar cover and make sure the tiny squirrel cage fan is spinning, or if it's clogged up with spiderwebs.
I think even if it auto-engages the recirculate mode, the display on the control module doesn't say so. Even when it's on auto-max, the blower still isn't on the absolute highest speed, and you can override that manually.
What I miss that I heard the Escalades and possibly Tahoes have is auto-blower-speed-reduction whan a hands-free call came in on the Verizon/On-Star interface. Now the Roadiemobile is no longer a DD, I gave that cell line up to save $10 a month, and just use a separate Bluetooth speakerphone.