this is already fixed... although, the man page is overly verbose about the older MQ policy.  I think we'd rather people simply used the default SMQ.  This output is from 6.9.

   Cache policy

       The  cache subsystem has additional per-LV parameters: the cache policy
       to use, and possibly tunable parameters for the  cache  policy.   Three
       policies  are currently available: "smq" is the default policy, "mq" is
       an older implementation, and "cleaner" is used to force  the  cache  to
       write back (flush) all cached writes to the origin LV.

       The  "mq"  policy  has a number of tunable parameters. The defaults are
       chosen to be suitable for the majority of systems, but in special  cir-
       cumstances, changing the settings can improve performance.

       With  the  --cachepolicy  and --cachesettings options, the cache policy
       and settings can be set when creating a cache  LV,  or  changed  on  an
       existing  cache  LV  (both  options can be used together).  The current
       cache policy and settings of a cache  LV  can  be  displayed  with  the
       cache_policy and cache_settings reporting options:

       lvs -o+cache_policy,cache_settings VG/CacheLV

       Example
       Change the cache policy and settings of an existing cache LV.
       # lvchange --cachepolicy mq --cachesettings \
            'migration_threshold=2048 random_threshold=4' vg/lv1

       lvm.conf(5) allocation/cache_policy
       defines the default cache policy.