Depends which embassy you're applying with. Hanoi didn't ask me for a contract since I supplied them and updated the certificate of work (more recent date, the better) which details how long I've been working with company + monthly salary + screenshot of company Linkedin which shows it's a globally remote team.
Hanoi approved quite a few worktation routes. Perhaps there were error in their applications? I wouldn't completely disregard it as option as it certainly is still one of the fastest embassies (granted all ducks in order) to approve, alongside Jakarta and Cambodia .