Why is my script telling me there's a process running when it's actually not?

Question

func () {    
    local arrayOfParams=$@
    local CMD="ps aux | grep -v grep"
    
    for item in ${arrayOfParams[@]};
    do
        local CMD="$CMD | grep -e $item"
    done
    
    echo "Current process PID : $$"
    
    echo "`date`: CMD is -> $CMD"
    local isProcRunning=`eval ${CMD}`
    if [[ 0 -eq `echo "$isProcRunning" | wc -l` ]];
    then
        echo "`date`: Following process is running: "
        echo "$isProcRunning"
        echo ""
        if [[ "$FORCE_RUN" == true ]];
        then
            echo "`date`: User forced the run of current process ..."
            # we extract the PIDs of proces mathcing our search criteria
            PIDS=(`echo $isProcRunning | awk '{print \$2}'`)
            for PID in "${PIDS[@]}";
            do
                # we extract the command running on said PID so that we know what we kill
                local PIDCMD=`ps -o cmd -p ${PID} --no-headers`
                echo "`date`: Killing PID: $PID with CMD -> $PIDCMD"
                kill -9 $PID
            done
            
        else
            echo "`date`: Current process will exit!!!"
        fi
        
        exit 0
    fi
}

The above code is meant to check if current process is already running .

I use ps -ef and grep based on some params which should be found under CMD

I remove the line coresponding to the current PID and then I expect the wc -l to return 0, but it's returning 1.

I run that line outside of the script and I get 0 indeed.

Any idea why this is happening ?