This is the fist data we've seen in the full frame mirrorless market with more than one brand active, and it is only the percentage of sales to one brand or another over that period in one country - not number of units in hands, not the total number of units moved, and not necessarily reflective of people switching between brands. We don't know if the increase in marketshare for Canon/Nikon is due to new entrants to the full frame mirrorless market, or movement from Sony. It is really hard to determine true marketshare from this data, but it does indicate that Canon had a better start than Nikon since they both start from zero.
As we've seen plenty of times before, camera manufactures get a huge uptick in sales when they release a new body. We saw full frame market share leaders flip between Canon (October 2017), Nikon (January 2018), and Sony (August 2018) over the last 13 months, coinciding with each company releasing a full frame camera shortly before (6DII, D850, A7III). It makes sense that Canon would receive that many sales, but whether sales continue will be more telling.
With that said, I got to play with an EOS R last week and while it seemed fine, it didn't knock my socks off, but I'd chalk that up to lack of familiarity with the body. The lens offerings are what make the R exciting to me - the fact that Canon is making RF lenses that they couldn't/wouldn't for EF makes the R an enticing product. I would bet that adding a higher-end model will pump the tires on those sales quite a bit. Time will tell.