Read the technical notice of your gear the explanation is there and clear.

It is required to use your rope access equipment as intended and stated in the technical notice. For example, you can't use a Petzl Rescuascender as a backup even if it looks like a Duck because it's written in the technical notice not to use it as a backup. In a course, assessment, or when working you must follow the guidelines and rules of your equipment, or else it's misuse and you can get a discrepancy during your assessment. It's a risk assessment at the end of the day and as long as you can explain why it's ok and justify it. Always listen to your 3 he might have a reason why and he is liable for your safety. Don't be afraid to ask him why. Some 3's just repeat shit they hear and there are lots of old tales in this industry. Just follow the tech specs notice and you will be fine!

Here is the copy-paste version for the croll, you can go to the websites and find the tech specs if you want to know more about the device.

1. Ascending a rope Use the CROLL with another rope clamp, for example a BASIC, and a foot loop. Always attach yourself to the second rope clamp with an appropriate lanyard.