I think it's just that the intermediary years are estimations and the chart isn't compensated.

The estimates are just bad and not adjusted historically. Doesn't make the chart bad... just makes the data a little wonky.

The intermediate years use statistical methods that better address some of the practical difficulties in getting complete and unique responses; the "actual enumeration" is well-known to be less accurate (in fact, the same methods used for between census estimates are also used by the census bureau to produce and publish estimates of the over- and under-counts in the actual enumeration.)

There was (probably still is, despite the fact that it seems to be a lost cause) a movement to use the better methods for all purposes, but given that it would be a constitutional change and the errors benefit the already politically powerful, there is pretty much no chance of it happening any time in the foreseeable future.

OTOH, I don't know ow that that actually has anything to do with the chart at issue: there is no information on sources or methodology, just "sources of this data are coming soon". If you don't have the sources ready to cite, you have no business publishing visualizations of the supposed data.

It sounds like you're inventing reasons to post-hoc rationalize bad data. What exactly are the intermediate years estimates of? What does "isn't compensated" even mean in this context?

Doesn't make the chart bad... just makes the data a little wonky.

The chart is great. It perfectly represents exactly the data in the tabular form. The data is apparently garbage though.