One thing I'd like to point out is that far from an extinct form, there are Sanskrit poets even today who can compose verses subject to such constraints, and at least two of them[2] even do it “live” on stage—compose with any of the classical constraints, on any given topic!—without pen and paper, as part of a performance[3] interleaved with many other interruptions.
Edit: About the verse in the title, just now found a Facebook post[4] that points out it's part of at least 10 such two-consonant verses in that chapter (which also has verses subject to various other constraints).
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[1]: I was not the original creator (https://en.wikipedia.org/w/index.php?title=Shishupala_Vadha&...), but added most of the content (https://en.wikipedia.org/w/index.php?title=Shishupala_Vadha&...): 90% according to the “Who Wrote That” extension.
[2]: Shatavadhani Ganesh https://en.wikipedia.org/w/index.php?title=Shatavadhani_Gane... and Shankar Rajaraman
[3]: https://en.wikipedia.org/w/index.php?title=Avadhanam&oldid=9... – excerpts from a recording of such a performance are at https://www.youtube.com/watch?v=m3GnorRNjXE though it's best experienced live!
[4]: https://www.facebook.com/sanskritsense/posts/438163406786809