A problem about 'Heuristic Setting'

System Version: Win10 x64
Norton Version: NS22.5

DETAILS: There are two different virus samples, and the two samples were detected by Norton as "Suspicious.Cloud.5" and "Trojan.Gen.2", respectively. (Under default setting"AUTO")

                 However, after I adjust heuristic detection setting to 'HIGH' ,which means norton can be more aggressively scan designated files, and restart to scan the both samples, strange thing happened, Norton detection result changed, telling me the two samples are safe. Therefore, I adjust heuristic setting to "AUTO" again, and scan them, norton successfully detected the two virus.

                So, my question comes: according to norton's description about heuristic setting, shouldn't the latter heuristic setting 'high' detect more threat? but actually norton didn't do that.