Is it good or bad practice to publish metrics with a value of 0 if they haven't been seen in a paritcular time window

See discussion here kamon-io/Kamon - Gitter But the tl;dr is that Kamon (a tool for measuring and reporting opentracing spans) reports the fact that a particular span HASN’T occurred. See > select * from "span.processing-time"name: span.processing-timetime - Pastebin.com for an example.

My question is, is this a bad practice?