I don't have a good explanation as to why the "fraction of terms" for DE is going down. But the decline seems to be coincident with the general decline in tech

I don't have a good explanation as to why the "fraction of terms" for DE is going down. But the decline seems to be coincident with the general decline in tech hiring, so my best guess is that the DE role tends to be a bit more internal facing than other software engineering positions, so it is probably an easy target for hiring freezes. Based on my personal experience, the DE team seemed to always be the last team to get approved for additional hires, as the other teams in the engineering org where more directly tied to revenue generating initiatives whereas we were often seen more as a cost center. But I don't think this is a long term trend. The DE role was originally tied heavily to the rise of data science, but it has turned into more of an operations role since then. You can probably get away with slowing down hiring for a little while, but just like with janitorial services, if you cut back too much things are going to get messy.