The idea of the eggcorn database is that these are descriptivist linguists - they believe language already existed anyway and they're just explaining an observable phenomenon, not somehow dictating what is or is not English. Some of these changes just remain forever considered mistakes. If you woke up a hundred years from now the chance everybody calls the little things which fall from oak trees "eggcorns" is negligible, they're acorns, you've misheard.
But on the other hand it's possible that in 2124 everybody considers "bi-election" normal as duh, there was an extra election, that's two, so bi-election, losing the analysis which got us the current word "by-election".
There are eggcorns related to the manor/ manner distinction, in particular "bedside manor" seems like a pretty obvious misanalysis. But you're correct that both "to the manner born" and "to the manor born" are considered reasonable idiomatic English.
