I'm surprised by how polished this version of Tetris appears to be, given it's for a word processor with a monitor that doesn't do the art of the game the justice it deserves.
In 1988, BPS produced Tetris for many computer platforms in Japan, including FM-7, MSX2, PC-8800, PC-9800, X1, X68000, and Family Computer (NES). Some of these are NEC products. By 1991, when the word processor version was released, Tetris had been ported to even more machines including TRS-80, Amiga, ZX Spectrum, and Macintosh.
https://en.wikipedia.org/wiki/List_of_Tetris_variants
So I imagine the high polish of the game is due to existing industry experience and references.
It would be interesting to make it playable through qemu on archive.org