It's not a bug, but I do think it's not expected behavior.

I did not expect the auto picked recipe to change after unlocking a more advanced tech, and it does not change consistently as you expect based on the input signal.

As you say, there are alternatives

Wire a combinator to a crusher, configure crusher to set recipe based on signals, send asteroid signals. The idea being you're telling the crusher what recipe to pick, based on what asteroids you've found.

Before unlocking advanced asteroid processing this is what the crusher picks based on the ...