It's a common fallacy among tech folks to believe that every decision can be made from 100% deterministic grounds ("X decision will result in Y percent change"). In reality, successful decision-making often involves speculation. The speculation in question is within the bounds of reason. You may disagree, but the fact that it is speculative isn't the problem.

And not acting while doing the whole analysis to reach close to 100% deterministic grounds mis a decision in itself! It’s perfectly reasonable to drop support for bun, and potentially revisit later on when more details come up