Hey 7th, how ya been?
Perhaps they are trying to ensure that even a weak signal will still work. Imagine that the pulse is at the end of a synth and connected to a couple servos and several LEDs. And the battery is getting weak. VCC and the signal line get as high as 3 and a half volts, maybe. This circuit looks like it's designed to provide a readable pulse under those conditions. Maybe a mosfet would have been better than the bc847bs?
I'm lookin' at my copy of Mim's*Timer Circuits* book, and he uses less ohms for higher current applications. He triggers transistors with as little an no resistor, and up to 10K, for decreasing current loads. The LV321 doesn't present much of a load, right?
OK, more questions than answers. But this a device with a very wide range of applications, so things like current constraints are limiting. Perhaps the designers got carried away.
No matter the cause - I like your easy fix! Can you detail it out here, or maybe post it in the Inventions area? I think we should encourage activities beyond hooking bits together.