Yes, stitching has to be done in post, I would want to do it that way anyway.Nice photo. I assume the stitching was done in post and not in the camera? And from raws or jpgs?
jpgs in this case. I always take raw+jpg. I only need to use the raw when things are very wrong, like colour balance, burnt out highlights etc. For me that is perhaps 1 in 100 photos, the rest of the time I use the jpgs. (I come from the days of Kodachrome slides where exposure had to be accurate to 1/3 stop and there was no postprocessing.)
One can only stitch (or stack) jpgs or TIFs and not raw. Software that claims to do it simply does its own raw conversion (without user control) and then stitches. I could have used the raw images, processed them to jpg or tif, and then stitched. But I simply used the jpgs, they are usually so good it makes no difference.