The DECscope User's manual (EK-VT5X-OP-001, 4th printing, March 1977) states (page 19) that Reverse Line Feed is VT52/VT55 only:
Reverse Line Feed (VT52 only)
invoked by ESC I (033 111)
However, vt50h termcap/terminfo entries, dating back at least to 2BSD (1980), include reverse linefeed. (vt50 termcap/terminfo entries do not).
$ infocmp vt50h # Reconstructed via infocmp from file: /usr/share/terminfo/76/vt50h vt50h|dec vt50h, cols#80, lines#12, bel=^G, clear=\EH\EJ, cr=^M, cub1=^H, cud1=^J, cuf1=\EC, cup=\EY%p1%' '%+%c%p2%' '%+%c, cuu1=\EA, ed=\EJ, el=\EK, ht=^I, ind=^J, ri=\EI,
Did the VT50h support reverse linefeed?