RF encoding introduces significant noise to the video signal because it moves the signal up to an area of the spectrum that is much more susceptible to interference. A monochrome 240p video signal of the best quality will be defined by its dot clock frequency at ~14 MHz. This would create a good quality 80 column text image as seen on machines like IBM CGA or Amiga. For RF compatibility, such a signal would be promoted to the TV VHF spectrum, which resides in a large and noisy range of ~50 MHz to ~250 MHz. Here, the signal is subject to interference from the many other signals present in the VHF spectrum. Thus, even without any distortion from the frequency shift (not possible), the quality of the signal as is transmitted to the TV is significantly degraded by noisy spectrum interference. Naturally, the TV also has to shift the signal back down to the native frequency as well, and this too is imprecise.
So you have noisy artifacts introduced through both the up and down frequency conversion needed for RF transmissions to the TV, and you have the fact that you are moving the signal into a much noisier spectrum band where it is interfered by other signals.
Therefore, yes, any avoidance of RF encoding, even for a basic text-only monochrome display, will benefit the display quality. Examples of bypassing RF encoding to achieve better results using a monitor are readily seen amongst various early computers, including the 1977 Apple ][, Commodore PET, and TRS-80 Model 1, all of which relied on bypassing RF for more readable text displays on monitors.
In my opinion, TV sets as computer monitors was never meant as a practical alternative to a monitor if you were utilizing anything other than low-resolution color output, probably for games. The fact that early computers supported RF was more for keeping the costs/barriers to entry lower for the target home market, since virtually all homes already had one or more TV sets. It's the same reality that has always applied to home game consoles, where the output capabilities improved almost lock-step with the capabilities of low-cost consumer display devices (e.g. "TV's") to the present day.