«وَاكْتَفَى مُسْلِمٌ بِمُطْلَقِ الْمُعَاصَرَةِ»
Imam Muslim was satisfied with contemporaneity for the relevant continuity inquiry.
The intended setting presupposes that a meeting was possible, that a reliable bar to hearing has not been established, and that complications such as tadlis must still be addressed separately. Mere overlap of broad dates when contact was impossible would not establish a sound link.
The difference is not that one compiler cared about continuity and the other did not. Both required continuity; they differed in the strength of evidence needed to infer it in the relevant muʿanʿan setting.