The difference is that a general purpose database typically organises data by fixed-size pages, so new data could be anywhere in the file as there is no guarantee of page ordering with regard to inserts. Whereas a specialised file format for logging would add new records at the end of the file (or in a circular fashion, depending on the design). But will have features similar to a database like a defined schema, and some form of indexing. This is true of systemd journals and Windows event logs anyway.
You can do the same kind of indexing with text files too, eg you see this with dictionary and thesaurus databases.
Thus if you're going to sacrifice the "read anyway" ability of a log file then you really need to go for a fully optimised database to really take advantage of a binary format - rather than this half-and-half approach that has none of the real benefits of either but all of the same drawbacks of both.
