I've started splitting my espresso shots (20g in, 40g out) as I've noticed my favourite cappa recipe contains only 15-20 g of espresso. This therefore allows me to taste every espresso shot I pull - great learning experience.

I have noticed, though, that the split single espresso always seems to taste quite thin compared to when the full double is pulled into a single cup... and I can't for the life of me figure out why. In my mind, as long as the spouts appear to pour evenly (they do), there shouldn't be a discernible difference between a combined double or a split single, provided the extraction parameters are the same.

Have others experienced this or have an explanation for it?