Why doesn't Spring Cloud use bootstrap.yml by default anymore?

Question

This is my Spring Cloud test project. As the java version is 1.8, I try to build the cloud project with some new version.

<properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
    <java.version>1.8</java.version>
    <mysql.version>8.0.30</mysql.version>
    <mybatis.version>3.0.0</mybatis.version>
    <mybatis-plus.version>3.5.2</mybatis-plus.version>
    <spring-boot.version>2.6.11</spring-boot.version>
    <spring-cloud.version>2021.0.4</spring-cloud.version>
    <spring-cloud-alibaba.version>2021.0.4.0</spring-cloud-alibaba.version>
    <alibaba.nacos.version>2.0.4</alibaba.nacos.version>
    <freemarker.version>2.3.31</freemarker.version>
    <swagger.version>1.6.2</swagger.version>
    <lombok.version>1.18.8</lombok.version>
    <openfeign.version>3.1.5</openfeign.version>
    <loadbalance.version>3.1.4</loadbalance.version>
</properties>

enter image description here

https://github.com/Autrui/cloud_test

Then I get the problem. In order and user module, I use bootstrap.yml to config name and nacos, it actually worked. But in gateway module, at first, I set the port 10010 in bootstrap.yml, but the gateway still runs at port 8080. The configuration in application.yml worked.

Then I Google and found that Spring Boot disabled the bootstrap.yml after 2.4.0. Then I have three problems:

1. If the bootstrap is actually be abandoned, why my order and user modules can work as usual?

2. I find we can add the bootstrap dependency in pom, then bootstrap will be loaded again, but I think this is not a elegant way to program.

config:
  import:
    - optional: nacos:order-dev.yaml
    - nacos: order-dev.yaml

I try to use spring.config.import, but IDEA shows Cannot resolve property 'optional' in java.lang.String. How can I replace bootstrap in my project?

3. Why Spring disabled the bootstrap? I didn't find the reason also don't know why.