If you are getting Kernel Panics (aka crashes) after a clean install or firmware Restore with no third party software installed and no migration/restoration from a backup, then it most likely means there is a hardware issue that needs repaired. Having Google Chrome should not really matter since so many people are using it on macOS without any problems.
An experienced tech knows the diagnostics rarely reveal hardware issues...it is really nice when it happens, but most times they do nothing for us.
It helps if the issue is fairly easy to reproduce so that they can actually see it themselves, but you can try showing them the Kernel Panic logs to show there have been crashes after the firmware Restore and just Google Chrome being installed.
It can be hard to get an Apple tech to take it seriously since Apple does not train them to look at Kernel Panic logs, but they should take it seriously if the crashes occur after a firmware restore. If they won't listen or do anything, then do you have any other local Apple Authorized Service Providers available in your area to see if they might take it more seriously?
I can tell you being a tech that a tech always prefers to see the issue first hand as it may provide clues to which part should be replaced, however, I am unusual in that I will look at the Kernel Panic logs for clues as well and use other means to try to identify even the smallest oddity as it may be related to the client's issue. Unfortunately Apple has very specific steps for their authorized techs to follow and for some this is all they know about troubleshooting computers. Keep in mind part of the problem is if the tech guesses wrong, then the customer will be upset that they paid for a repair which did not solve the problem...for a problem which is difficult to reproduce this is a real problem. For a problem easily reproducible it is less of an issue since the tech should know within a certain amount of time with testing if the problem appears to be gone. I can tell you from the tech's perspective, intermittent failures, especially ones hard to reproduce, are just as frustrating for us.
