The system property "hudson.consoleTailKB" is supposed to control how many KB of console log is shown in the default console view.
It is used in two places:
Both jelly scripts expect a method getSystemProperty(key) on the Functions class. But that method does not exist. Therefore the default of 150 KB is always used and the system property is ignored.
The fix is available in this PR: https://github.com/jenkinsci/jenkins/pull/3200