Fast opamps tend to have low open-loop gains, like 60 dB maybe. So if one needs precision, and gain is set by available 0.1% resistors, some sort of secondary gain fine-trim is prudent.
R22 can up the gain a little, as needed.
Sometimes, app notes and data sheets add a small resistance to the otherwise-grounded non-inverting input of fast amps. This has been explained to me as a "damping resistor", possibly to kill wire-bond resonances. As long as R15 is there, I may as well add R22 for the gain tweaker.
Actually, R22 *reduces* the gain, but it will work anyhow. I can pitch the gain high with the R14/R13 ratio or something, and then trim it down.