The 100th Le Mans was absolutely fantastic!
Ferrari's biggest advantage to running the Hypercar programme was it got to avoid a lot of extremely expensive layoffs that would have forced it to be highly uncompetitive in F1 (since it would not have been exempt from the cost cap, while nearly all expenses relating to the Hypercars are instead on the Hypercar budget). However, having them work part time in F1 while on the endurance payroll would be just about the worst way to do it, since this would inevitably get flagged up as an anomaly (if nothing else, the part-timer has to be granted access to the F1 data, and doing that to someone with no ostensible reason to have the access is going to alert auditors). Better to have an acknowledged and plausible part of the F1 payroll and simply underestimate the amount of time spent doing F1 vs non-F1 projects, if one wishes to do that sort of cheating.
Technology transfer is nearly impossible to police, but then again it's also nearly impossible to police technology transfer from sister teams, component providers and car manufacturers, which covers every team except Williams and possibly Alfa Romeo already.