Coinsandcanada.com

Looking at this site seems like prefixes stopped at AUN for Thissen Crow was any prefixes used after AUN

That's not what it says at all.
It gives no range of prefixes, only prices for those notes with a premium above the default amount in the top line.

The last Theissen-Crow prefix was EBX so there were many prefixes after AUN.

Catalogues only single out prefixes that are more collectible/sought after rather than regular prefixes.

Here's the scoop on the AUG to AUN $2.00 according to my 2019 Charlton:

The Thiessen-Crow signature combination was intended to begin with $2 note AUK1640000. However, notes with the Thiessen-Crow signatures have been discovered in series AUG to AUN. Those of series AUJ are very scarce, while series AUG and AUH are extremely rare with the Thiessen-Crow signatures.

-Page 301

In the next paragraph, Charlton discusses another "ANOMALY OF THE BIRDS SERIES" with the Crow Bouey EPW & the Bonin Thiessen HNB prefix (on the $5) & the editor compares the discovered anomalies to the EET "Good-Overs" discovered on the earlier 1971 $10. In other words, the newer Thiessen-Crow signature sheets were somehow mixed up with the older Crow Bouey AUG-AUN run, so no real solid data exists on how many of these notes exist. That is why even the Crow Bouey prefixes are collectible but the rare/scarce ones remain Thiessen-Crow notes.