Resolving the placeholders(with default value) of XML BeanDefinition in the Configuration Class

The previous one #6543 has been closed by @mercyblitz with comments "fixed in 2.7.8". However, this issue still exist in both 2.7.8 & master.

[X ] I have searched the issues of this repository and believe that this is not a duplicate.
[X ] I have checked the FAQ of this repository and believe that this is not a duplicate.
Environment
Dubbo version: 2.7.7 & master
Operating System version: linux
Java version: JDK8
Steps to reproduce this issue
update https://github.com/apache/dubbo/blob/master/dubbo-config/dubbo-config-spring/src/test/resources/org/apache/dubbo/config/spring/demo-provider.xml
from

to

run testProviderXml() in https://github.com/apache/dubbo/blob/master/dubbo-config/dubbo-config-spring/src/test/java/org/apache/dubbo/config/spring/schema/DubboNamespaceHandlerTest.java
Expected Result
UT should pass

Actual Result
UT fail as flow:
java.lang.AssertionError:
Expected: is <20813>
but: was <8080>
Expected :is <20813>
Actual :<8080>

This issue may related with previous issue or change:
#6035
#6079