> If they could say how inaccurate the current maps are they could have made maps that were accurate to begin with.

It's very possible to know something within a given uncertainty, still be able to quantify that uncertainty, but not be able to completely eliminate that uncertainty. If we take for example the paleomagnetic measurements underlying many paleogeographic reconstructions, it is definitely possible to estimate the uncertainty, and propagate that uncertainty into uncertainty in paleogeographic locations (e.g., Heslop & Roberts, 2020). The extent to which that uncertainty can be reduced will be fundamentally limited by both epistemic (which we can reduce by collecting more data) and aleatory uncertainty within the paleomagnetic measurements. Additionally, there will be a fundamental limit in terms of how much we can reduce the epistemic uncertainty because of the limited availability of preserved rocks. Not all steps in paleogeographic reconstructions lend themselves to as direct uncertainty estimation as the paleomagnetic components, but it's not fair to say that there is no way to characterize uncertainty in these products.