Hello and welcome,
If I'm not wrong, yes, this is how it works, it will poll the storage container each poll interval and list the files in the container to know the files it needs to download and process.
It is mentioned in the documentation that this can get expensive if you have a large number of files.
Polling is generally recommented for most cases even though it can get expensive with dealing with a very large number of files.
I don't think so, this is how polling work when consuming data from blob storage, this is the same thing as polling on S3 or GCS, with large buckets it can get expensive.
One alternative would be to change your data pipeline and put your logs inside an Event Hub instead of storage containers.