Let me clue you on a few secrets.

1.) “InfoSec” is a concept that can conceivably encompass the entire IT staff. Don’t get twisted thinking it’s a specific subset, because it will just keep unfurling forever if you treat it that way, and you’ll be stymied.
That was me. I am you.

2.) At the Operations level, there is no difference between senior systems administration, and Security. They are precisely the same thing.
You must understand the system and its quirks, design durable delivery, hedge against edge-cases you don’t know about, and deliver precision

If your senior systems administrators are not delivering confidentiality and integrity and assurance, they are not at the highest levels of the profession.
Pretty much every “security weakness” has a corresponding operational failure mode they permit. It’s indistinguishable.

Why do you think people think I’m good at Security, when my primary job experience is spending ten years trying to reduce Helpdesk ticket counts?

It’s an identical continuum. Quality and Security are the same god damn fucking thing.