To clarify, the number 3.41% has significance in the sense that a pokemon would be used enough in a tier to be seen a certain number of times when facing an opponent out of an X number of battles. It isnt too high, to the point where "crappy" or niche stuff would remain OU (such as mandibuzz and Mamo), and it isnt too low that everything and its evolution tree is in a specific tier.
Also, direct data tiering has NOTHING to do with borderline (BL). If something did not meet the 3.41% cutoff in OU, it would directly go to UU. BL is a place Tier Councils use to place pokemon deemed "too strong" for the tier. Hawlucha, by direct data tiering, should be UU or lower. However, the UU council has suspected Hawlucha and came to a general agreement that it is sinply too strong and lacks a fair amount of checks and/or counters for it to be healthy to the metagame.
For a mon to drop out of BL and into the tier it was originally banned from, the tier council must be willing to resuspect the pokemon, usually after tier shifts (every 3 months), when a number of mons either leave the tier or drop down to it or the addition of a new clause. Such is the case with Venemoth, whose brokeness in UU was being a great Quiver Dance Passer in a tier with powerful special attackers such as Nidoking and Hydreigon. Now, thanks to the new Baton Pass Clause, Venemoth has lost its primary usefulness in being a Baton Passer, and is being allowed in UU for the time being unless it is found to be overpowering (unlikely).
Also, for a mon to leave BL and go a tier up, all they must do it achieve the 3.41% cutoff, which happens every 3 months.
Usage data only transfers a pokemon through Official tiers.
Suspect tests remove a pokemon (or in the case of Megas, stones) from an official tier into a borderline tier, an in between of the tier it dropped from and the tier is was suspect tested out of.