AWS Parameters and Secrets Lambda Extension lifetime

I came to know that AWS Parameters and Secrets Lambda Extension has been launched recently to improve the application performance as it decreases the latency and the cost of retrieving parameters and secrets. Source:- https://aws.amazon.com/about-aws/whats-new/2022/10/aws-parameters-secrets-lambda-extension/

The above link also states that "This lightweight and easy-to-use extension caches parameters and secrets, and persists them throughout the lifecycle of the Lambda function".

So does it mean that this extension creates 1 instance per 1 lambda instance. For e.g. say I have a lambda that has an input as customerid. Gets me the customer phone number from the back-end API which is authenticated via credentials stored in secret manager.

if I receive 5 simultaneous requests to this lambda I would have 5 instances of lambda. Would I have 5 instances of the extensions or 1? And if no requests are received for the next 1 hour I believe all lambda instances and extension instances are de-allocated?

if yes, what is the benefit of using this extension over storing the secrets in a global variable in the lambda? (read the secret onto the variable for the first time from the secret manager)

Thanks Hari