

It’s likely CentOS 7.9, which was released in Nov. 2020 and shipped with kernel version 3.10.0-1160. It’s not completely ridiculous for a one year old POS systems to have a four year old OS. Design for those systems probably started a few years ago, when CentOS 7.9 was relatively recent. For an embedded system the bias would have been toward an established and mature OS, and CentOS 8.x was likely considered “too new” at the time they were speccing these systems. Remotely upgrading between major releases would not be advisable in an embedded system. The RHEL/CentOS in-place upgrade story is… not great. There was zero support for in-place upgrade until RHEL/CentOS 7, and it’s still considered “at your own risk” (source).
Not the person you replied to, but I’m in agreement with them. I did tech hiring for some years for junior roles, and it was quite common to see applicants with a complete alphabet soup of certifications. More often than not, these cert-heavy applicants would show a complete lack of ability to apply that knowledge. For example they might have a network cert of some kind, yet were unable to competently answer a basic hypothetical like “what steps would you take to diagnose a network connection issue?” I suspect a lot of these applicants crammed for their many certifications, memorized known answers to typical questions, but never actually made any effort to put the knowledge to work. There’s nothing inherently wrong with certifications, but from past experience I’m always wary when I see a CV that’s heavy on certs but light on experience (which could be work experience or school or personal projects).