It seems to me it was more of a case of DR asking to go because he’d been advised by Cas that we wouldn’t be renewing his contract. Milnes seems key to this decision, not Miller.
Miller has played better of late and may well have another year to go on his contract so not as easy to off-load.
Feel for DR a loittle, after everything he’s gone through but it may well turn out to be the correct mveo for all.