Hi,
Can you please share AAA and tacacs configuration of your ASA?
Additional to this, when you check the ACS reports under "Monitoring and reports" section, is it showing you are hitting the exact same rule than switches?
Now, the read only access would be determined based on the commands you authorize on the ACS "Command Sets", so if you do not have command authorization enabled on the ASA, even if you hit the exact same rule, it will never perform command authorization against the ACS and there will be no deny for the non read-only commands.