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.
