Spring boot application listens on IPv6 without parameters -Djava.net.preferIPv4Stack = true and -Djava.net.preferIPv4Addresses

My question is about a Spring boot jar. When running a can on a production machine like:

java -jar xyz.jar

He is not responding to my request. Because it is listening on ipv6.

But when I run my application as java -jar xyz.jar -Djava.net.preferIPv4Stack = true -Djava.net.preferIPv4Addresses

He answers my inquiries.

Is it the production machine configuration that makes the application listen on ipv6, or are there other reasons?

Luckily -Djava.net.preferIPv4Stack = true
-Djava.net.preferIPv4Addresses
parameters solved my problem. But I'm confused !!

Note. Tomcat is used as an embedded server.
Spring Boot version 1.5.4 RELEASE