You should have a base awareness of the tools that your team is using. It's the same for product managers, which is why some of the best product managers come from engineering backgrounds.

Do you have to be as good as your team members at their skills? No, of course not.

Going to be hard to justify hours, timelines and other managerial duties to the people that you report too as a manager if you don't know if your team is working efficiently.

Just my two cents.

The major problem here is that looks like there are not really a developer team behind, but just the Senior Developer. No designer and no others person who make good stuffs on photoshop or others grapic design tools.

"How long is this photoshop task going to take you?"

"A least a week"

Manager that knows little about photoshop: "OK"

Manager that is proficient in photoshop: "Really? Looked like a 2 day job to me"

Asshole manager that knows shit: asks one of your colleagues leaving out some details so he'll get a lower estimate, then tries to commit you to that timeline.

"Do you know how to develop software?"

No.

"Then how are you going to manage me? Exactly."