I concur. I'm quite certain it says that you cannot yield from within a looping structure. From the Help page "Scheduling APIs":

>> Important This API is not supported within JavaScript array iteration functions (such as every, filter, forEach, map and some). JavaScript array iteration functions are designed to be executed as a whole. SuiteScript cannot yield in the middle of these control structures. To work around this limitation, use a for loop or the forEachResult(callback) function. For more information about nlobjSearchResultSet.forEachResult(callback), see forEachResult(callback).