As there are multiple KASAN modes that all work differently, it makes sense to mention the enabled mode in the "KernelAddressSanitizer initialized" message. Something like:
kasan: KernelAddressSanitizer initialized (generic)
kasan: KernelAddressSanitizer initialized (hw-tags, mode=async, stacktrace=on)
Done for arm64 in . Other arches only support the Generic mode, so having different messages doesn't apply.