Effects of "ssh_clear_authorized_keys" in chained packer builds

I am using Packer to build AMIs for EC2 instances.
I am trying to use “ssh_clear_authorized_keys” in my packer build to ensure that the keys do not show up in the EC2 instances built out of my AMI.

My final AMI is built using a series of Packer builds chained together
For example:
AMI A is the base image, AMI B uses AMI A, and finally AMI C uses AMI B to get the final image.
I am setting “ssh_clear_authorized_keys” to true in the packer.json for AMI C.
When I issue a “cat authorized_keys” command, I see one key still showing up.

Note: without the “ssh_clear_authorized_keys”, I get 3 keys.
Can someone help me understand where this key is leftover from?

In general, I would like to better understand the workings of this field.

Thank you,

Closing this out.
I needed to set the field in all the builds.