Currently the install version only will have users downloading and installing to, what is likely, the drive they want to recover from.
This will result in data erasure.
Even with the portable version I'd think there would still exist the possibility of things going completely wrong especially on the system drive with just the general running of Windows itself. Recovering from a secondary drive, or external/portable drives with no OS may fair much better without things being generated by Windows like logs, prefetch data (just running Recuva will cause Windows to automatically create prefetch data for it, registry data is likely too since it like to keep a record of what programs have been executed), etc., that could possibly overwrite a file that someone needs to recover.