Again, this is a terminology and definition problem. The backup sets (all files being backed up in the set) are incremental forever. In other words, you back up all files in full only the first time, and after that, you back up only those files that are new or changed. Those subsequent backups can be a backup of the entire file or just the parts of the file that changed. The type depend on whether you are scheduling block-level backups. If you are, then some of the files may be subsequently backed up block-level with just the file changes backed up. Or, if the file is small, we may just back up the entire file again. If you are not using block-level backups, then we back up the changed file in full each time.

When you're talking about individual files, then yes, you need to run a periodic backup of the entire file (now called Incremental in the current release). I know the terminology is confusing, but don't get hung up on the terms. Just know that you should schedule block-level backups if you are backing up large files and want to take advantage of the ability to only back up changes within those files. Schedule the incremental backup less frequently.

If you do not need block-level, leave that setting off. From a scheduling perspective, if you're using block-level, you might schedule them once a day and then schedule the incremental backup every 14 or 30 days. You can adjust as needed.

I understand what you are saying. "Full" during the very first backup means an exact copy of all folders/files in the entire backup set. "Full" during subsequent (incremental) backups means an exact copy of only new or changed files. (ignoring block-level for simplicity)

This all seems reasonable and I would not be worried or confused except that when I read the documentation for incremental at:
https://www.cloudberrylab.com/resources/blog/incremental-backup-guide/
Which states:
"Forever incremental backup decreases recovery reliability"
"It also becomes harder and takes longer to recover the whole dataset"
"periodical full backups are highly recommended to start the new sequence of incremental backups"
"An incremental backup approach has several drawbacks...Less data consistency and reliability"
"backup software analyzes the whole incremental backup chain. If one element in that chain is corrupt, your data is non-recoverable"
"The flaws of this backup type such as slower restore and dependence on the increments integrity may be addressed by performing the full backup periodically"

This documentation seems to say that incremental is NOT RELIABLE unless a "Full" backup (meaning a new exact copy of ALL folders/files in the entire backup set) is performed occasionally.

That's just a general blog post and not one related to the product specifically. It does not apply to what we're discussing.