meh, eu encontrei uma solução realmente hacky usando outro método concat.
$resizedVideoList = file('resizedVideoList.txt', FILE_IGNORE_NEW_LINES);
$inputStringForConcat = "";
$concatString = "";
$concateNvalue = 0;
foreach ($resizedVideoList as $key => $value) {
//$limiter++;
//if ($limiter > 2)break;
$inputStringForConcat .= " -i ".$value;
$concatString .= "[$key:0][$key:1]";
$concateNvalue++;
}
$concatString .= " concat=n=$concateNvalue:v=1:a=1[v][a]";
echo ("<pre>");
print_r($inputStringForConcat);
print_r($concatString);
echo shell_exec("./ffmpeg $inputStringForConcat -filter_complex '$concatString' -map '[v]' -map '[a]' concatenated_time.mp4 2>&1");