Yes.  The statsd configuration is what drives which percentiles will be
seen in timers.

I don't see the immediate value of restricting them.  If we choose the
percentiles we expect, then we rely on users matching their statsd
configuration to our expectations, which would require more work.

Also, by just accepting the percentiles given to us, we allow the user to
control what gets stored if, for example, they are only concerned with 99th
and not any others.