I checked AWSCloudFormation dynamodb documentation and since PointInTimeRecoveryEnabled is optional, what would be the default value if it is not provided?
Yes, it is false in the code documentation.
(property) PointInTimeRecoverySpecification.pointInTimeRecoveryEnabled: boolean
Indicates whether point-in-time recovery is enabled (true) or disabled (false) on the table.
@default
false