Earlier quoted context omitted.
To me what I hear: your pipes weren't supported and your pressure is too high if it can be described as violent. I can hear my old office's script telling me to sell you a PRV or two.
I hear what you’re saying but isn’t it a bit of six of one and half a dozen of the other? The high(er) pressure relative to what the pipes could withstand exacerbates the effects of water hammer induced by the pressure washer’s solenoid constantly slamming open and shut in the matter of milliseconds, no? Lower pressure (via a PRV or otherwise), higher-rated pipes, slowly opening and closing valves, or strategically i…
If your question is can those gas piston water hammer arrestors protect fixtures-- sure, I mean that part is just physics. Whether it's worth it before a hosecock is a completely different matter -- also as per the OP you're far more likely to break a toilet valve just from handling than from water hammer.