I can confirm that TestComplete seems to work just fine with the svn.exe supplied with Tortoise.
It does NOT need the one specified in Help Page. Indeed, Tortoise is ALL you need and T/C will find the path all by itself.
The reason that I didn't have the utility on my PC is that the command line tools are disabled (by default) in the Tortoise Installer - so if (like me) you have been using Tortoise for years and don'thave svn.exe - just re-run the Tortoise installer selecting the option.
Tortoise is indeed installed and working. I think it is recommended because it (tortoise GUI) provides the additional features we've all come to know and love (indeed, rely on) for comparing builds etc.
It appears that in addition to tortoise TestComplete also needs the command line utility svn.exe - to provide the integration with T/C menus. This utility is not part of tortoise and the (TestComplete) setup won't complete without it. The link posted on the Smartbear page now takes you elsewhere, as do Google searches for the same thing. I believe all I need is a single .EXE (but the RIGHT one).