Yes, but the contract is signed at the beginning of your employment which may be years ago. You need a current letter that reaffirms that you are actually doing all the things that your contract stated. It's not uncommon for people's job duties to change over time even if they don't sign a brand new employment contract. For example, when you get a raise, you don't sign a new contract. Or perhaps you move to a new office location. Again, you don't sign a new contract.
In addition, the letter will have your manager's or HR manager's name and contact information on it. They are endorsing it and IRCC may call them to verify the information.
The person who countersigned your contract may be long gone from the company and even if still there, may not have any idea who you are. Again, in large companies this is not uncommon.