Is it recommended to wipe the whole laptop before returning it ?
It depends on how paranoid you are. Recommended by IT? No. Recommended by most people? Yes.
First, the whole disk is encrypted by BitLocker (Windows) or FileVault (macOS) so most people can't unlock it and access your data. IT can unlock it and decrypt it, but why would they want to?
Second, the asset team is supposed to wipe and reimage every laptop before returning it to the leasing company. They're not going to decrypt it and look at any files on it. They'll simply wipe it and install a fresh image and be done w/ it.
But, since humans make mistakes, I typically wipe my laptops and re-image them before returning them just because I may have minor personal data on it. I had a manager that asked me to wipe all the laptops on our team before they got shipped back as part of the refresh process, especially his and the project manager because they had PII for employees and contractors on their laptops.
I only had one problem w/ one Windows laptop. I wiped the drive and did the SSD low level format and then re-formatted it as NTFS via a bootable USB stick. When when booting from a Windows installer stick, it kept complaining about not having the necessary drivers to use the drive and I was unable to find the proper SSD drivers from either the Internet or Lenovo. After 4-6 hrs of fighting it, I just returned it w/ a blank, formatted drive.