HGR Displays During HBL?

["Bryan Parkoff" <none@nospam.net>]

    You may notice magenta (deep red) color appears in the screen during 
HBL.  You can type below like this in Applesoft BASIC prompt.

]HGR
]HCOLOR=5: HPLOT 279,0 TO 279,191
]HCOLOR=4: HPLOT 0,0 TO 0,191

    Do you notice that orange vertical line becomes brown in the far right? 
I know that it is cut-off, but did you see magenta vertical line in the far 
left?  If you fill 0x40 in memory address: 0xXXFF, it will fill magenta 
vertical line from line 0 through the middle line.
    It has a bug on Apple II+, but Apple //e has fixed the bug.  Can you 
please explain why Apple II+ has reproduced bug for curiousity?  0xXXFF can 
have data, but they are not supposed to be displayed during HBL which it 
must always be undisplayed.  It is how magenta vertical line detects 6th bit 
of data bus which it is turned on to form magenta vertical line while 
vertical line in position 0 is always filled with 0x80 (delayed black).
    Is it possible that the designer made mistake to design Apple II+'s 
motherboard with TTL chip?

Bryan Parkoff