I hadn't noticed that... wonder if it's new. Just downloaded the Armv8-M ARM (nice acronym) and... this might be helpful, but man extracting this stuff from a PDF seems error-prone and the wrong way to do it.
replyThey first published the Armv8-M ASL around 2017.
replyI suspect you've believed that this didn't exist due to the predominance of pre-Armv8-M devices in the market: there is no ASL for Armv7-M and earlier, and devices based on these older cores remain extremely common (STM32F1x, etc.) The good news is this is changing as new devices appear. The bad news is there probably will never be ASL published for older cores.