Do you have a specific link or download for the AHAB Application Programming Interface Reference Manual if one exists. If not, then the HAB Version 4 Application Programming Interface Reference Manual and is there difference to be noted for AHAB?
The App note for the secure boot using AHAB for the i.MX8X is available at the following link: https://www.nxp.com/docs/en/application-note/AN12312.pdf
And you can refer to the security reference manual after request in the following link: https://www.nxp.com/webapp/sps/download/mod_download.jsp?colCode=IMX8QXPSRM&appType=moderatedWithout...
Hope it helps!