Why does this method call work, but not in lining the code?

So in this method, the conditional for the while loop is something that I chose to remove as in line code and create a method which is called when needed. However, this first method does not work, and causes the application to silently lock up.

def getLineRows( rows, index ) {
    def lineRows = [rows[index]]
    def newOperator
    def i = index + 1
    if ( index <= ( rows.size() - 1 ) ) {
        newOperator = false

This is the code in question.

        while ( index <= ( rows.size() - 1 ) && !newOperator ) {
            if ( rows[index].PGM_PROC_OPE.trim() == "" ||
                ( rows[index].PGM_PROC_TY == "OR" ||
                  rows[index].PGM_PROC_TY == "AN" ) ) {
                lineRows << rows[i]
            } else {
                newOperator = true
            }
            i++
        }
    }
    return lineRows
}

In this second, and visually identical method, I have simply created a method called moreRows(rows, index). There are two other method calls, however they have been eliminated from consideration through testing.

def moreRows( rows, index ) {
    return index <= ( rows.size() - 1 )
}

What would cause this code below to function properly when the moreRows is used, rather than the method above, where moreRows is in line?

def getLineRows( rows, index ) {
    def lineRows = [rows[index]]
    def newOperator
    def i = index + 1
    if ( moreRows( rows, i ) ) {
        newOperator = false
        while ( moreRows( rows, i ) && !newOperator ) {
            if ( operatorEmpty( rows, i ) || isSpecialProcType( rows, i ) ) {
                lineRows << rows[i]
            } else {
                newOperator = true
            }
            i++
        }
    }
    return lineRows
}