What's the overall calcium percentage in that feed...is it higher than the usual ~3-5%?
Wonders if the OS in it is large chunks or.....?
If all the birds laid softies it might be worthy, but 'on the side' lets those who need more get it without overloading those that don't.
OS really shouldn't be mixing in to the feed, especially if it's layer feed.
better to have it in a separate feeder so only those in need will eat it and you can keep an eye on consumption.
I use this jar for a OS and egg shell feeder...