Differences between EL 2.1 and 2.2

The answer is in the EL 2.2. specification document. Here’s an extract of relevance:

A.1 Changes between Maintenance 1 and Maintenance Release 2

The main change in this release is the addition of method invokations with
parameters in the EL, such as #{trader.buy("JAVA")}.

• Added one method in javax.el.ELResolver:
  • Object invoke(ELContext context, Object base, Object method, Class<?>[]
paramTypes, Object[] params).

• Added one method in javax.el.BeanELResolver:
  • Object invoke(ELContext context, Object base, Object method, Class<?>[]
paramTypes, Object[] params).

• Added one method in javax.el.CompositeELResolver:
  • Object invoke(ELContext context, Object base, Object method, Class<?>[]
paramTypes, Object[] params).

• Section 1.1.1. Added to the first paragraph:

  Simlarly, . operator can also be used to invoke methods, when the method name
  is known, but the [] operator can be used to invoke methods dynamically.

• Section 1.2.1. Change the last part of the last paragraph from

  Upon evaluation, the EL API verifies that the method conforms to the expected
  signature provided at parse time. There is therefore no coercion performed.

  to

  Upon evaluation, if the expected signature is provided at parse time, the EL API
  verifies that the method conforms to the expected signature, and there is therefore
  no coercion performed. If the expected signature is not provided at parse time,
  then at evaluation, the method is identified with the information of the
  parameters in the expression and the parameters are coerced to the respective
  formal types.

• Section 1.6. Added syntax for method invocation with parameters. The steps for evaluation of the expression was modified to handle the method
  invocations with parameters.

• Section 1.19. Production of ValueSuffix includes the optional parameters.

No other changes are mentioned. So, it’s indeed just only the method invocation capability.