In SQLite, a database file can be 140 terabytes, https://www.sqlite.org/limits.html
And reading and writing can be even faster than if they were stored directly in the filesystem, https://www.sqlite.org/fasterthanfs.html
And reading and writing can be even faster than if they were stored directly in the filesystem, https://www.sqlite.org/fasterthanfs.html
Even if you can in theory save some time with small files with sqlite, you would be back to read/write IO and userspace/kernel byte buffer switching.
And it probably wouldn't be faster than something like a mmaped file anyway (unless the SQLite Db is also mmaped).
https://www.sqlite.org/src/doc/trunk/src/test_onefile.c
https://www.sqlite.org/vfs.html
IIRC, during one of his talks D. Richard Hipp mentions this actually being done for real.