Cognito phone number validation error

"I have 2 user pools:

User pool 1: ・Created by someone else via the AWS console.

User pool 2: ・I'm trying to view creating a clone of user pool 1 using CDK because I want to manage it with source code. When I check on the console, user pool 1 and 2 have the same information, both requiring phone number attribute. However, when I use the AWS SDK v2 to create a user, if I set the phone number to an empty string, I can successfully register on user pool 1, while user pool 2 encounters the following error: Attributes did not conform to the schema: 2 validation errors detected: Value at 'userAttributes.phoneNumbers.member.complexListValue.1.member.value.member.stringValue' failed to satisfy constraint: Member must have length greater than or equal to 1; Value at 'userAttributes.phoneNumbers.member.complexListValue.1.member.value.member.stringValue' failed to satisfy constraint: Member must satisfy regular expression pattern: [\p{L}\p{M}\p{S}\p{N}\p{P}\t\n\r 　]+

My goal is to create a 100% clone of user pool 1 using CDK, but I don't understand why user pool 1 does not validate phone number length, as there is no setting for this. I have diffed the YAML but they only differ in identities (user pool 1 does not have, user pool 2 does have):

• AttributeDataType: "String" DeveloperOnlyAttribute: false Mutable: true Name: "identities" Required: false StringAttributeConstraints: {}