Why can the iPad also receive text messages received on an Apple mobile phone?

You can just log out of your iCloud account in settings

1. Because you use the same Apple ID, if you use iMessage to send text messages, as long as it is the same Devices with Apple ID will be able to receive it. Just log out the device ID that you don’t need to receive. It feels like sending text messages through iMessage is similar to email

2. First of all, iPhone, iPad and Mac all belong to Apple. The company's products, so the systems used are Apple's IOS and Mac OS systems. These two systems are related to each other. Messages sent between Apple devices can also be sent through operators using Apple's own iMessage. Implementation

3. If the iMessage function is turned on on both iPhone and iPad, and you log in with the same Apple ID account, the messages sent will be displayed simultaneously on all devices.