In my opinion, the standard for the pull-up should be one where the chest touches the bar, always. When your arms go over your head, there are muscles that shorten to rotate your scapula upwards. When one group of muscles shortens, another group lengthens. This is referred to as an agonist vs antagonist relationship. Therefore as your arms go over your head, there are also muscles that must lengthen to allow the upward rotation of the scapula. This relationship switches at the top of the Supinated Chest to Bar, where the downward rotators of the scapula fully shorten, and the upward rotators fully lengthen. This ROM standard also demands extension of the thoracic spine, whereas chin ups allow for the rounding/kyphotic posture that many of us display as people privileged enough to spend excessive time in a seated posture. Most who have the strength in elbow flexion to do a chin up still lack the strength of full downward rotation and extension. Supinated Chest to Bar Pull ups should be equal to Dips in reps/weight and both should be ~65% of the Back Squat. Wide Grip Pronated Pull ups are ~5% less capacity than Supinated. Importantly, if you cannot yet do BW Pull ups or dips, use a Gravitron machine where you can use measurable assistance. Bands are not measurable!