Maybe you’re saying you’re 30% BnR playing the ghost 8-ball on a 7 ft table. I could see a good 475-500 doing that regularly, maybe not all the time, but it would happen.
Most of my pool is played against the 425-525 range on bar boxes [Diamond tables, 4.5" pockets, Simonis-like cloth speed but a knockoff]. No one in that range is coming close to a 30% BnR rate on 8-ball. Closer to 525 they are likely to get out first time at the table if the opponent breaks, makes 5 balls, and then scratches, but even that's not a guarantee if there are still 2+ problem balls on the table.
Issues:
Cluster busting is still a problem at this level.
Bar boxes are harder for pros than 9 footers for 8-ball, since the number of clusters and problem balls will be higher
People in the 475-500 range are still good for tanking about 1 in 10 "easy" shots.
People in this range know they have to solve their problems, so they end up likely to miss when they have to try to 3-rail power follow a shot
Also:
A 20% BnR rate is in the Fargo 700 range on a bar box. Maybe 650. One reference: I play with a Fargo 519 who has only 7 BnR in APA with over 300 APA matches (so over 1500 APA racks). Granted he was an SL-6 a few years ago so it may be more heavily weighted toward his earlier years.
In the old APA app, we used to be look up people from other areas, but I guess the APA got tired of us cross-checking Fargo ratings so they took that away from us! (I was going to check Parks and others).
That said, anyone 400+ "Can" make every possible shot on a bar box, can put together a good highlight reel, and is likely to have at least 1 BnR on the books (either in practice or in a match).
EDIT: Found another comparison - A Fargo 600 with 250 lifetime matches (more than 1250 APA racks) and only 28 BnR in APA (2.2% BnR rate).