why does tortoise, wcng and cygwin break from icon caching?

Today Random Person on #svn reported a problem and later its apparent
solution, and it struck me as rather peculiar:

[[[
<yates`> when trying to do an svn cleanup, i get a strange message:
svn: E200030: disk I/O error, executing statement 'COMMIT TRANSACTION;'

this is under win7 using the cygwin svn client
and also tortoisesvn is installed

...

<yates`> neels: i found the issue

strangely, there is an interaction between tortoisesvn and the cli svn under
cygwin

you must disable tortoisesvn's icon caching, then the problem goes away.
http://www.mail-archive.com/cygwin@cygwin.com/msg123745.html
]]]

and

"I've confirmed what others have stated that it's only a problem with
v3.7.12.1 and NOT a problem with v3.7.3."

Hmm, disable icon caching to not break wc-ng? Why!?

~Neels