In A500, the address decoding performed by the Gary chip could be
disabled with the /OVR override signal for certain address spaces
only, but not the area which used by this hack. But it seems to
be work in practice.

In the Commdore Amiga A500/A2000 Techical Reference Manual, page 93:
"
The /OVR, override, signal is a special Amiga expansion signal that
can serve two purposes. The signal can basically turn off the on-
board decoding of system memory ranges. As a result of this, it can
also turn off internally generated things, like /DTACK.

The timing in the A500 and B2000, based on the Gary chip (not the
PALs of the older machines) effectively prohibits the use of OVR*
for the area outside of $200000 and $9FFFFF.
" 
... it continues to say that to use this signal for 
tristating the /DTACK is better supported.