I don't know that sieboldianum is as cold hardy as pseudosieboldianum. It is most common on Kyushu, in a warmer climate. We've never had a problem with either species here, though that's not saying much. The variegation on 'Kumoi nishiki' really doesn't look chlorotic at all. It is a "splashed" or "speckled" variegation, so it never looks unhealthy. Certainly a very beautiful maple. It's quite a robust grower, but seems more tender than the species. Here, ours suffered heavy stem damage in the 2021 late frost, which was quite deep. You wouldn't know it to look at the top this year, but the bark died over 180 degrees, and several inches.