The question of whether or not an offender would abuse his victim in front of a witness is somewhat academic...
...by the 1980s, internal complaints about the problem had reached a point wherein the WTS was compelled to slightly revise the two-witness rule to to classify the first accusing victim as "witness #1" and a second accusing victim as "witness #2", so an actual third-party eyewitness to a single offense was no longer deemed necessary (in no small part because poorly-informed loyalists already had difficulty believing that something like this could even happen, so extreme skepticism amongst elder bodies was the norm, rather than the exception).
Nevertheless, the Org has held so strongly to their interpretation(s) and application of the two-witness rule, NOT because they want to follow so-called "Biblical" standards, but because they've come to depend on it it as a crucial tool in keeping the nature and full scope of the problem from the rank-and-file (plus a century of internal rhetoric and propaganda has made capitulating to any outside pressure an absolute anathema).
Yes, they want to avoid negative publicity, lawsuits, and the expenses both incur, but even more so, the endemic and institutionalized nature of the problem thoroughly undermines their claim of being "God's Exclusive Earthly Organization" like almost nothing else*...
...because, let's face it... despite what some may claim, actually being an active, dutiful JW isn't really all that enjoyable... so without that particular carrot/stick combo, there's virtually zero real incentive for the average rank-and-filer to actually stay.
...
*Not to mention that, in a huge dollop of irony, the staunch application of their previously mentioned "Biblical" standards are arguably making the problem worse...
...and therefore casting doubt on said standards' efficacy and legitimacy, which is pure poison for any organization who derives their authority from the Bible.