Because Send Anywhere app for Android only displays the files in your internal storage, deleting the Send Anywhere app on your Android device will not delete the files you receive. Rest assured, the files you receive are stored on your Android device.
However, if you delete Send Anywhere app for iOS on your iPhone/iPad, the files stored in the Files tab of the Send menu will also be deleted. This is because all files on the Files tab of the Send menu are files that are stored only in Send Anywhere app. iPhone/iPad users should be aware of this and make sure to back up files stored in Send Anywhere folder in the native Files app before deleting Send Anywhere app on your iPhone/iPad.