MAX BOOST it's just like you described. If you gave a high-quality cooler, your AMD processor (and Intel too, with their TurboBoost) will work on that (for 5600X is 4.6Ghz, yes) maximum freqency without any problems.
If you have bad-quality cooller (or even use stock BOX), MAX BOOST performance (mean, freqency) will be achieved only at the start of stress tests and etc, at that small time amount when processor just started work on 100%, and temperature are slowly (or not so slowly) growing up to 95 degrees. When 95 (or 100/105, check AMD specifications) temperacure achieved processor lover it's frequency, and going to balance it, for still use maximum of power, but no hotter than 95/100/105 degrees.
Hope I ansvered your question.