Yes, it does incentivize this. But it disincentivizes something even worse (attaching penalties to honest testimony). There is no perfect answer here. All we can do is choose what sort of adverse outcome to want to minimize. US law tends to lean toward it being better to fail to penalize wrongdoing than to penalize innocent people.

That said, if someone is giving testimony that is intentionally deceptive such as lying and saying it was a mistake, making stuff up -- which is lying -- or even being deceptive without uttering an untruth, that is something that can be penalized.

The pros engage in perjury by just saying "I don't remember". It may be a lie, but good luck proving that.