The premise underlying the "update" requirement is based on the documentation that you are (continue to be) GE eligible. Allowing a change to these data online using a secure server, as is allowed for passport information as well as mail-to information suggests that protection from identity theivery is not the CBPs concern. The CBP informs, per their expressed protocol, participants using their website (you log into your account) and by mail to the individuals US mailing address.

It is still unclear whether or not employment history updates are required to be done and if so, if they need to be done in person. How CBP can verify that the employment information in your current profile is correct s something I dont see as possible absent associating the GE data with your IRS data.

What I do know is that the update of passport and drivers license information is based on expiry dates which are documented within the GE dataset. It is a "no brainer" to have GE eligibility tied to a "within date" DL and passport absent any need to look at external data.

I addition, US passport data are imbedded as part of DHS making electronic verification an automated process if necessary or desired.

After that - how do they know and why does it matter?

Looking forward to hearing OPs answer to the question - do I need to update my employment data and if so, do I need to visit a CBP office to do so.