Transitive dependency with a bom - maven

Question

I have a project named P1 which is a spring-boot project.
The pom has already a parent pom, so I decided to use springboot with a bom.
<dependencyManagement>
<dependencies>
<dependency>
<!-- Import dependency management from Spring Boot -->
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-dependencies</artifactId>
<version>${spring-boot.version}</version>
<type>pom</type>
<scope>import</scope>
</dependency>
</dependencies>
</dependencyManagement>
This project is then deployed as P1.jar
Then I have a 2nd project named P2.
This project has only 1 dependecy which is the P1 project :
<dependencies>
<dependency>
<groupId>my.company</groupId>
<artifactId>p1</artifactId>
<version>${project.version}</version>
</dependency>
</dependencies>
Here is an extract of mvn dependency:tree for both project :
P1:
[INFO] +- org.springframework.boot:spring-boot-starter-data-jpa:jar:1.4.3.RELEASE:compile
[INFO] | +- org.springframework.boot:spring-boot-starter-jdbc:jar:1.4.3.RELEASE:compile
[INFO] | | +- org.apache.tomcat:tomcat-jdbc:jar:8.5.6:compile
[INFO] | | | \- org.apache.tomcat:tomcat-juli:jar:8.5.6:compile
[INFO] | | \- org.springframework:spring-jdbc:jar:4.3.5.RELEASE:compile
[INFO] | +- javax.transaction:javax.transaction-api:jar:1.2:compile
[INFO] | +- org.springframework.data:spring-data-jpa:jar:1.10.6.RELEASE:compile
[INFO] | | \- org.springframework:spring-orm:jar:4.3.5.RELEASE:compile
P2:
[INFO] +- org.springframework.boot:spring-boot-starter-data-jpa:jar:1.4.3.RELEASE:compile
[INFO] | +- org.springframework.boot:spring-boot-starter-jdbc:jar:1.4.3.RELEASE:compile
[INFO] | | +- org.apache.tomcat:tomcat-jdbc:jar:8.5.6:compile
[INFO] | | | \- org.apache.tomcat:tomcat-juli:jar:8.5.6:compile
[INFO] | | \- org.springframework:spring-jdbc:jar:4.3.5.RELEASE:compile
[INFO] | +- javax.transaction:javax.transaction-api:jar:1.2:compile
[INFO] | +- org.springframework.data:spring-data-jpa:jar:1.10.6.RELEASE:compile
[INFO] | | \- org.springframework:spring-orm:jar:4.2.9.RELEASE:compile
As you can see, the spring-orm dependency differs.
Can someone explains me how this works and how can I fix that ?
At the moment I added the BOM in my 2nd project. But it's not my goal.
I want to be able to import P1 project with its REAL dependencies without having to do anything else or know which bom the project is using.