Good morning Eat
I have been a little busy last two days to pen my pieces.
On your hypothetical scenario, while it may not be prosecutable given the difficulty in proving what is essentially a "domestic" scenario, coupled by the legal application of the de minimis rule ∼it is nonetheless an ethically conflict of interest scenario, which should be avoided.
This culture of quid pro quo breeds the 贪小便宜 mindset, especially amongst the older generation, and is still prevalent amongst the younger folks. It should be strongly discouraged.
Have a great day elder brother. XOXO