This warning was nessecary when the mass replay checker was first implemented; it was *extremely* slow. Even on V10.13.18, while hugely faster than when the feature was first introduced, it's still slow enough that it's worth having the warning.
On V12, however, the mass replay checker is generally very fast - not as fast as the Lix one, but still, fast enough that running a mass replay check on Lemmings Plus I (which has 150 levels, and uses 9 different graphic sets which almost guarantees there will be pieces being discarded from the cache regularly and thus reloaded later) takes well under a minute. I'd say that given this, the warning is no longer nessecary.
