Just take everything on online forms with a pinch of salt, same with my comments, haha. Some posts here I don't even understand cos it's not phrased in proper eng.
Anyway, just wanted to support you. What your article shows are just facts, really nothing to nitpick unless figures are grossly inaccurate. In choosing a starting date, small variations of a few days seems inconsequential to me. After all, when quoting the YTD performance of a stock, it is also against a single day as point reference.
Interpretation is up to the reader really. Some reits may have had poor performance this year, but did not take into account how they held up well in the first year of covid. Some reits performed well this year, but that may be because they were terrible last year and rebounded (and whether they actually rebounded to the level before their dip matters too). All these are the reader's responsibility to look into.