I have come across such "remedies" myself in the past (we can't really use the word "repairs" here, can we) ... just "making it work" (regardless of any safety features that may be overridden).
The devices definitely become true "creatures" in the Frankenstein style
I recall many happy(?) days spent trying to return x-ray (usually) circuits back to original states before fault-finding proper could commence. Doing that without circuit diagrams provided much extra "fun".
It's a vice that puzzle lovers share.
But I'm interested in the quote; what were they going to do? Board swaps?
I estimate that by inhibiting access to the diagnostic port they were hoping to prevent a review of the fault and its possible solution; so that his proposal was the "only viable one"