There aren't that many demos and bootlegs(also depends on anyone's definition of a bootleg), so that's a very accurate number.
There might be more than you think...
There are the Special HuCards (Gunhed Caravan, Soldier Blade Caravan, BMan 93, Final Soldier Caravan, Power League Gold, Bonk 3, Youkai Dochuki Gold, Darius Alpha)
and several "commercial demos" (Faceball, FEoE-SCD, Hudson RPG, Psychic Detective 3, Laplace No Ma, Bman 94)
and some store demos (DUO DEMO 1, DUO DEMO 2, PCE 4 game instore demo, Emerald Dragon, Kidou Keisatsu Patlabor-Griffon, Mad Stalker, Mamano Hunter Youko Tooki Yobigoe, Startling Odyssey, World Heroes 2)
And Mook Versions (Emerald Dragon, Anearth Fantasy Story, Kabuki Den, Lodoss Tousenki SCD, Xanadu).
The PCEngine Hyper Catalogs, and PCEngine Fan Specials, and DEVELO starter kits.
And the "unofficial commercial games" (the 3 "Excite Software" discs, the MindRec titles, the Games Express titles, etc).
Those are the ones that I know of -- most are included in those numbers, but not all.