I see tiny caliber pistols as the same way, a form of knife, to be used as an injection system of sorts while grappling, or close (a bar gun), but I got rid of my .25.
For 1.3 ounces extra in weight, 1.5 inches additional in length, and 1.2 inches additional in height, you can carry a 9mm.
The 9mm’s recoil and muzzle flash from a vest-pocket sized pistol can make it problematic to practice with.
Also, that 1.5x1.2x whatever width increase is not something that can be comfortably tucked in a boot or, in the case of my nurse friend, carried on a garter strap. The tiny Rohrbach R9 (which is what I think you’re referring to costs $1149. Out of the range of many people.
I think you forget just how small something like the Baby Browning is. A Baby Browning weighs a mere 9.7 ounces, is only 4.1 inches long and is just 2.8 inches tall.