Placing OB penalties in the field of play versus actual out-of-bounds at the property boundaries is weaker design and not in the core set of challenges in the traditional game of golf let alone placing them in blind areas of the holes. Trees and rough with 3 feet and higher foliage are our version of sand traps and rough in ball golf.
With respect, I think you're way off the mark here.
The concept that only property boundaries should be OB, else it is automatically weaker design, is frankly arbitrary and near-sighted. There's so many opportunities to create doubt, fear, the illusion of choice, or force a very difficult choice in a players mind using OB. I also believe that the majority of disc golfers around the world disagree with you. Many of the highest rated courses in the world have sculpted OB, and many of the most prestigious tournaments (as determined by the pros) are played on those courses. I don't think the data supports your assertion at all.
Height of foliage is also not equivalent to sand traps/bunkers. Trees are still used in golf, for the same purpose, to change the angle of attack.
Bunkers are designed to change the maximum distance you can get on the shot out of them, as well as make the lie of the ball more difficult. So if we equate lie of the ball and loft of the club into disc golf terms, you're talking speed of the disc and ability to run up - or restriction of power by forcing 1-steps or standstill throws. Trees are one way to do this, but not the only way. Bunkers in disc golf are obstacles that force you to throw lower speed discs...in fact low foliage does the opposite, it forces you to disc up.
The core set of challenges in golf and disc golf are exactly the same, to complete the course in as few attempts (strokes, throws) as possible. The design elements hinder the ability to do that quickly. OB is a design element.
To not use woods lines and rough that way when available (no cliffs, of course) detracts from the game of golf that challenges players to recover versus directly penalizes them. We don't get to see the recovery skills of the players which are typically the most viewed highlights. Even the promo pics for the DGPT and DGWT each show a guy putting from his knee because it's visually more interesting.
I think you're making a correlation that's not parsimonious. Promo pics are usually chosen because they display an emotion, without the dreaded "huck face" pictures that unfortunately always appear on the front cover of discgolfer magazine.
It's too bad we're seeing this expansion of OB penalties skewing what's considered good design for top players. Ball golf dialed way back on penal design elements like this in the mid-1900s for good reason, it's not fun for players. Plus, challenge elements versus direct penalty elements also keeps competition closer for more drama.
Honestly, it sounds like you're making this stuff up. I don't want to beat up on you, but the most famous golf courses in the world are the most penal.
The Old Course
Augusta National
Pebble Beach
In the 90's we went through "Tiger Proofing" courses, courses were made longer, more narrow, and more challenging.