I came across offer letters that mention not taking any leaves during the notice period, and if they do, the notice period is extended. Some companies mention that leaves can be taken with manager approval. Most managers approve leaves out of courtesy. I also came across employees who utilize all of their earned leaves during the notice period once they complete the KT or avoid KT as a gesture of hatred towards the company.
If the issue is regarding knowledge transfer then, To improve knowledge transfer in an organization, I would suggest having regular knowledge transfer sessions every six months. This would allow employees to become aware of the work done by other employees in their department or team. The notes from these sessions could then be shared with subordinates, providing them with a learning curve and helping them to understand the different roles and responsibilities within the organization. For critical, important, or niche skills or roles, knowledge transfer sessions should be conducted more often.