Speaking as a leader of software teams, some cross training is nice in order to spread knowledge and insight but I’d prefer to have team members be subject matter experts in their disciplines.

I'm not sure if people will get the reference 😅

its a great control mechanism, to not allow someone to become a subject matter expert in more than one discipline. Hence the modern "goal" to be in a vertical big corporate.

I would never disallow or punish or force.