No, it is not required.  The arrival date you provide should represent the earliest date you plan to arrive, but you have the flexibility to arrive later. Unless you obtain a visa extension, the departure date indicated is the last day you are allowed to stay in the country.
Here's an example:
Suppose you apply for a 1-month visa and arrive on January 1, 2023. Your visa letter will be valid from January 1, 2023, to February 1, 2023. You have the freedom to enter the country anytime between January 1 and February 1, but you must depart by February 1, 2023.
Please be aware that once the approval letter is issued, it cannot be modified. Therefore, if you wish to arrive earlier than the specified date on the approval letter, you must apply for a new approval letter.
It is crucial to plan your trip well and make adequate preparations. To prevent any misunderstandings, carefully review the Vietnam visa requirements before submitting your application.