This is total nonsense, the 13.8 V were not introduced simply for fun, that has its reasons. To generalize here and claim that a minimum supply of 12 V is now applicable to all radios is just as completely unrealistic. The previously mentioned disadvantages of modified power supplies, which were developed for a completely different purpose, should be well known. Discussing this is therefore a waste of time, especially if you also start mixing all mobile devices with HAM radios.
So if you're talking only about mobile devices, like the Yaesu FT-857, then it's just nonsensical to provide them with only the minimum voltage of 12 V for mobile use, if they are used only stationary anyway. The bandwidth for the supply of these devices is significantly larger in accordance with their design than with all other radios. That's why they are also more universally applicable and generally attractive. In fact, for this reason alone, a regular operation with 13.8 V is necessarily better than just with the minimum voltage mentioned. The use of a high quality power supply is therefore not only a question of money, but also of reason. The idea here to save costs, I think is just as perverted, as the minimum supply of an amateur radio used as a base station. Therefore, I maintain my statement, 13.8 V guarantee in all cases a much more stable and cleaner output power than with this Chinese crap, which would also need to be additionally modified so that it works in a theoretically usable voltage range.
In principle, radio interference of any kind should always be avoided first in one's own home, and not only in the neighborhood! It is unbelievable how much hypocrisy and false opportunism is displayed here when it comes to convincingly finding a justification, just to save a few bucks. Shame on you!
So I repeat:
don't use these cheap power supplies for the stationary operation of your amateur radio!