@sbwright @freehaiku
I’m not a complete authority but I actually think it was a bit the other way around.
As with the #HaroldStewart translation that you just posted, most of the early translations and haiku in English did not follow the 5-7-5 format.
#RHBlyth was probably the most influential translator of #haiku (four volumes, early to mid 1950s) and he did not do 5-7-5. #Blyth was the translation that #Ginsberg and #Kerouac had access to.
As to when, later, and why, 5-7-5 started to gain ascendancy . . . that is a fascinating question, but I don’t know the answer to it.