I noticed that my proxy recording sessions were generating far fewer timer elements than expected.

I consulted HTTP Test Script Recorder component reference and in the "Grouping" attribute, noticed mention of a potentially relevant JMeter property called "proxy.pause":

< http://jmeter.apache.org/usermanual/component_reference.html#HTTP%28S%29_Test_Script_Recorder >

I created a trivial test plan with a BeanShell sampler to log the runtime value of proxy.pause and it was null.  In jmeter.properties, an assignment for it is commented out with a note claiming a default of 5 seconds.

This is consistent with source file "/src/protocol/http/org/apache/jmeter/protocol/http/proxy/ProxyControl.java" (both 2.13 and today's trunk):

    private static final long sampleGap =
        JMeterUtils.getPropDefault("proxy.pause", 5000); // $NON-NLS-1$
    // Detect if user has pressed a new link

However, documentation (linked above) states default as 1000 milliseconds (1 sec).

Either sources (.java and .properties) are incorrect or doc is incorrect; I'm not sure which.