Andrew, has you actually talked to Martin Sorrell about this issue? Quoting a 'warning' isn't quite the same thing. Sorrell is an accountant by training not a marketing guru. A bloke that lives by numbers. You have demonstrated that in an imperfect world, he has good data on which to model his business. If he knows 52% of adverts are never seen by humans, he knows 48% are and can adjust his model accordingly.
Like many of your posts, this one indicates you want to live in a perfectly fair and honest world. We all do but sadly other humans are not so obliging. In the absence of a perfectly fair world, honest and reliable data about its unfairness is very helpful.
Interestingly you don't quote the same statistic for last year or the forecast for next year. If the number of ads seen by humans will be 48% today, 90% tomorrow and 20% the day after that will be a problem because these numbers are not useful for their predictive value. However if the numbers are 48% today, 47% tomorrow and 46% the day after, then fluctuations can be accommodated.