I think essentially the position is that sins should always be confessed to an elder but in not all cases would the matter go to a judicial committee - in some cases a couple of elders would just give "strong counsel" and let the matter lie.
About ten years ago when I was an elder myself and another elder once were summoned by a young pioneer couple who had been married for a few years & decided to fess up that they had been a bit naughty before being married ( not full intercourse but pretty much everything else. ) They deliberately chose to confess to us as we had a reputation of being kind & discreet ( so they said. )
We were very wary of sharing this information with the rest of the BOE as some were hard liners who would remove them from being pioneers & maybe even form a JC & others had very gossipy wives who were bound to find out via pillow talk and blab to everyone in the congregation.
We weren't too sure what to do so we phoned the CO who basically told us just to keep it quiet & just tell them that as it had happened a few years ago & they evidently still had Jehovah's blessing ( yuk ) then it would go no further.
Another documented example would be viewing soft porn - eg *** w06 7/15 p. 31 Questions From Readers ***
Some Christians have become involved in the viewing of pornography. This is offensive to God, and the elders may be shocked that a fellow believer has done this. But not all viewing of pornography calls for a hearing before a judicial committee. For example, suppose a brother viewed so-called soft-core pornography on several occasions. He is ashamed, confesses to an elder, and is determined not to repeat this sin. The elder might well conclude that the brother’s conduct did not escalate to the point that he engaged in “uncleanness . . . with greediness”; nor did he display a brazen attitude, indicating loose conduct. Although no judicial action would be warranted, this type of uncleanness would call for strong Scriptural counsel and perhaps follow-up help from the elders.