This has nothing to do with FR! It has everything to do with being able to pull it through conduit without breaking the cable. So a turn radius is an important parameter, so you set the pipe bender correctly. You bend and install the conduit and then pull the cable. Finding you can not pull the cables is a big oops! So to have that turn radius spec, is vital in drawing up your plans, building and laying out the conduit. If you are smart and don't want trouble you exceed the specified turning radius somewhat.
WRT bend radius, I'm actually referring to bandwidth and data throughput more than audio/video frequency response but with HD video, it does apply. For speaker wiring, it doesn't really matter unless it's being pinched.
FYI for those who consider installing their own data cabling, Cat5e maximum pull is 25 pounds. Exceeding that causes stretching and altering the twist rate. Cat6 and higher can be pulled with more force, but mot much more and it should be pulled carefully in all cases.
The bend radius I mentioned is for bare cable, where it could drop over/through/around framing and that doesn't mean the edges are rounded like the newer lumber, old framing had a very crisp edge. Cabling that won't need to be changed (voice/data infrastructure, typically) isn't always in conduit.
You're assuming the plans include this when almost nobody other than Low Voltage installers/contractors (the ones who actually care) and cable manufacturers (who may have been the ones who tested cables to find the effects). You may be thinking in terms of your residential experiences, but in conduit, the only real concerns are:
Does it have too many right angles? (Not supposed to exceed 180° total without additional pull boxes)
Does it have enough pull boxes on long runs (greater than 100')?
Will the cables snag on the joints?
Is the conduit filled to >65%?
Most contractors don't understand, nor do they generally care, about the care and handling of cabling- they want it done quickly and as cheaply as possible UNLESS they're a design/build firm that relies on repeat business.
You wouldn't believe some of the terrible work that's out there.