That is bizar...
I used cacls for te first time in a script with /T /E /C and /P (not /G)
It never asked me for a "y"es or "o"ui
While testing, without /T /E or /C, both /P and /G did ask for "y"es.
When adding /E (Edit the ACL, not replace the ACL) it does not ask for confirmation.
Is this for use during logon? I don't think a normal user can change ACL on the %WinDir% or %ProgramFiles%.