That’s true, but in many cases you can use the continuous query to move from one retention policy to another after it is collected. For example, I gather temperature data as it changes, and it goes into the 1 month retention policy. Then I use a continuous query to get the min/max daily and store those forever.
Also, you don’t have to use the persistence to store the data to InfluxDB. It is possible to POST directly from a rule. In that case you have control over the retention policy.
There’s some work on a new InfluxDB persistence binding here that mentions retention policy specification.