Editing reportDownloadTimeout in an ads.properties file does not set this parameter when using ReportDownloadInterface in client version >=3.1.0. To reproduce:

Set api.adwords.reportDownloadTimeout in ads.properties to a non-default value.

Add the line:
System.out.println(reportDownloader.getReportDownloadTimeout());
to
https://github.com/googleads/googleads-java-lib/blob/master/examples/adwords_axis/src/main/java/adwords/axis/v201702/reporting/DownloadCriteriaReportWithSelector.java

Run the example. The default value 180000 prints to the console.

Workaround: override by using .setReportDownloadTimeout after reportDownloader is instantiated.