I would like to see somebody explain this theory to me to see if it makes any sense. I've used 3 different types of polys (SPPP, Cyberflash and WeissCannon) and I've never seen any of those manufacturers say anthing about waiting 24 hours before play to help minimize tension loss. You would think if it would help, they would mention it, like how they mention about stringing 5-10% lower on polys.
The only thing I heard, and observed myself, is that you should expect some initial tension loss after a fresh string job, even before play. But I don't think there's anything magical about the first 24 hour period.
I've been charting my string tension loss with an ERT300 on several poly string jobs and it looks like the tension drop continues up to 10 hours of actual play before it stabilizes into a flat line. And the total drop is around 5-10% of the initial tension measure right after a string job.