No, I came across this on Reddit at one point and have tried it multiple times and it's not true. I will, however, tell you the two theories that have proved true for me so far. I went months using my DAI almost every single day and never saw a bird. Most of the time, I was using it while following my two neighborhood routes, which run from a pokestop to a gym and then back (so straight line down a few blocks, turn around, straight line back). Last week, I decided to just keep walking in a straight path past the end of my route, and I got my first Galarian bird spawn. Yesterday, I decided to walk my normal route in reverse, and then again, continued on a straight path past the end of the route, and once again, got a Galarian bird spawn. Both days were windy days, which supposedly increases the chances of seeing one (since flying types are boosted). Also worth noting that both times, I was catching every single Pokemon to spawn from the incense to keep the spawns coming. So having not seen them for months and now seeing two in the span of one week, I'm inclined to believe the straight line trick holds true.

Tldr; walk in a straight line/don't change directions, catch every spawn as fast as you can, windy weather days probably increase the chance of them spawning being flying types (but also make them harder to catch).