ok - I was not aware of that now I also understand why the description you posted is different from that what I saw in a snap that I had a look into manually.
Do you know this thread: InfluxDB+Grafana persistence and graphing ?
snap’s, dep’s and other type of distributions should be based on the same source code. Apart of distribution defaults the configuration should be similar. Please excuse in case I am too naive.
There is an influxdb.conf file included in the snap. I would start by checking if the default values match with the values that are described in the above mentioned thread.
As mentioned by rikoshak the config file is located at $SNAP_DATA/conf/influxdb.conf