This seems to be fixed in the most recent version (2.0b3), which I'm also running on one of my servers:
$ curl -H "Host:pool.sks-keyservers.net" "http://keyserver2.brian.minton.name:11371/pks/lookup?op=stats"
Hockeypuck OpenPGP Keyserver Statistics
Hockeypuck OpenPGP Keyserver Statistics
Taken at 2015-05-21T17:09:39Z
Settings
Version ~unreleased
Server Contact 0x0424DC19B678A1A9
HTTP ip6-localhost:11371
Recon :11370
Gossip Peers
Statistics
Total number of keys: 3941740
Daily Histogram
Day New Keys Updated Keys
2015-05-21 112 208
Hourly Histogram
Hour New Keys Updated Keys
2015-05-21 14 15 38
2015-05-21 15 32 66
2015-05-21 16 55 96
2015-05-21 17 10 8
$ curl -H "Host:pool.sks-keyservers.net" "http://keyserver2.brian.minton.name:11371/pks/lookup?op=stats&options=mr"
{"now":"2015-05-21T17:11:31Z","version":"~unreleased","contact":"0x0424DC19B678A1A9","httpAddr":"ip6-localhost:11371","reconAddr":":11370","peers":[{"Name":"peer1","httpAddr":"keyserver.brian.minton.name:11371","reconAddr":"keyserver.brian.minton.name:11370"},{"Name":"peer2","httpAddr":"keys.jhcloos.com:11371","reconAddr":"keys.jhcloos.com:11370"},{"Name":"peer3","httpAddr":"pgpkeys.mallos.nl:11371","reconAddr":"pgpkeys.mallos.nl:11370"},{"Name":"peer4","httpAddr":"keyserver.erat.systems:11371","reconAddr":"keyserver.erat.systems:11370"},{"Name":"peer5","httpAddr":"keyserver.pch.net:11371","reconAddr":"keyserver.pch.net:11370"},{"Name":"peer6","httpAddr":"aes.keys.peer.sh:11371","reconAddr":"aes.keys.peer.sh:11370"}],"Total":3941741,"Hourly":[{"Inserted":15,"Updated":38,"Time":"2015-05-21T14:00:00Z"},{"Inserted":32,"Updated":66,"Time":"2015-05-21T15:00:00Z"},{"Inserted":55,"Updated":96,"Time":"2015-05-21T16:00:00Z"},{"Inserted":11,"Updated":12,"Time":"2015-05-21T17:00:00Z"}],"Daily":[{"Inserted":113,"Updated":212,"Time":"2015-05-21T00:00:00Z"}]}