Whenever you run multiple 3 phase conductors in the same raceway, there is a potential for the expansion and contraction of one conductor's magnetic fields to induce a current on an adjacent conductor. But when all three phases come from the same source, even all the way back to the utility generator, these effects will cancel each other out.
But the output conductors of a VFD are being created from a NEW source, the DC bus and VFD transistors. So even if the VFD is putting out 60Hz, the sine waves of the outputs are not in sync with the sine waves of the input, so they no longer have the same cancelling effects. The same is true for multiple drive output cables, because if you have drives, you not only have outputs that are not in sync, but are at different frequencies altogether. The result is generally unpredictable, it CAN be devastating in that very high voltages get induced onto the cables and this can GREATLY exacerbate any reflected wave issues as well, which leads to insulation failure in the motors and/or the cables themselves. I witnessed one installation on a 250HP inverter duty motor that failed, it turned out that they doubled back on the cable tray putting the output cables with the input cables for just 25ft of the run, and the voltage spikes at the motor exceeded 2500V so even though the motor was made with 1600V insulation, it failed anyway. Or the cables can coexist fine for years with no noticeable effects. There is not way to predict, so the best policy is to avoid it all the time.
In cable tray if you can't avoid it, you bundle input cables together and output cables together (trefoil them) then separate the bundles by distances according to the current / field strength, upward of 3 feet, but most people using cable tray do so to AVOID having to mess with cable routing. Using shielded VFD cable helps with not having to worry about it as well, which is one reason people do that too. Whenever someone tells me that shielded VFD cable is too expensive, I respond with "Compared to what?" because doing NOTHING is expensive too, usually MORE expensive when you count down time costs.