There are 225 connections to the mongos, with 40 shards, each
with a 5-member replica set. lsof shows ~4600 open connections to the mongos process.
Trying to grow a buffer to 134 MB for the output of 4600 connections seems a little large (~32 kB/connection entry), but making the command scale is the goal.
Introducing a cursor to the command (and others like it) would allow it to work on arbitrarily sized clusters.