The MSX2 Technical handbook by ASCII states (in 3 different places) that :
"In screen modes 1 through 3, Y-coordinate was 209 for erasing the display of the specified sprite and was 208 for erasing the displays of the specified sprite and all sprites following it, but in screen modes 4 through 8, where the limit of Y-coordinate has been increased to 212 dots, the values to be specified are now 217 and 216, respectively."
I never heard before of that 217 Y-value for sprites ... I know of the 216 Y-value and the effect it has on sprites of higher plane number, but not that one. What bothers me is that the Yamaha manual for the V9938 VDP does not talk about it either.
Of course I understand that with a Y-value of 217 the sprite will not be on screen, but not generated and not on screen are two different things ...