Different behavior between 7 and 8 when parsing custom attributes.

Porting from Vaadin 7 to 8. I’ve got a line in an .html ui file:

In Vaadin 7 SDataSet.setImmediate(true) is called. In Vaadin 8 it is not. Changed immediate → immediately and setImmediate → setImmediately and all works as intended. Shouldn’t this be listed in the port guide someplace? Is there a list of reserved attribute names someplace?