Update February 16 (20 days later) the plant looks like it's still doing surprisingly well, even after having been planted out so early.
I was a little surprised.
This was going from inside under optimal growing conditions, with warmth and artificial LED light, to outside in practically the middle of winter. Other hardy citrus varieties that I have suddenly moved from growing inside to outside early in the year have not done that well. (The leaves turn yellow or patchy white, eventually fall off, there has been stem die-back sometimes, even when outside temperatures have remained above freezing)
To me, this seems to indicate remarkable resiliency. All the newest little leaf growth still appears green and healthy.
(However, this has been a good year, and almost all the other hardy citrus, even marginal varieties, appear to be doing very good left outside, having gone through the winter)
This looks like a plant that can handle sudden temperature change shock well.