Starting with 5.0.0, the dependency to the JMS API was changed in spring-jms for 2.0.
Spring documentation and/or javadocs might make clear that this does not mean that spring-jms 5.x actually requires the provider used to implement 2.0.
In my case, I am evaluating the impacts to upgrade some applications I have from spring 4.x to 5.x. For other external dependencies/impacts like for instance JEE APIs like servlet-api or JPA, Spring documentation make this clearer. For instance, LocalContainerEntityManagerFactoryBean's javadoc make it clear that JPA 2.1 is required. As I currently depends on a JMS provider (Oracle AQ) that only implements JMS 1.1, to be sure I would not have issues I had to download spring-jms code and search in it for calls to ConnectionFactory.createContext. Only after doing that I was able to see that there is no such call, and was able to conclude (yet without 100% certainty) that the upgrade of the dependency to 2.0 must have been to allow the spring-jms ConnectionFactory decorators to be 2.0 compliant.
Spring Framework Reference documentation and/or some javadoc (maybe the one of @EnableJms) might make this clear.