Only 100 webapps are detected : Maxcontext doesn't seem to be read

We're currently testing an architecture where we deploy 70 webapps in a 3-nodes cluster.
After some times wondering why only some of the webapps were visible in the /mod_cluster-manager URL, we discovered that a Maxcontext parameter existed and was defaulting to 100.

Then we set the Maxcontext parameter to 400, but it doesn't seem to change anything. Still only 100 webapp contexts are detected.

I tried having a look at the C source code, but I don't see anything obvious.
Maybe this parameter is just not read?

Thanks a lot for your help.