I believe they meant that a software-button (e.g. in the control center) would do the trick just as well - like with most other smartphones…
Unfortunately, "just as well" is debatable, if not pretty much incorrect.
A physical button for the often-used mute feature accomplishes several functions beyond just changing the mute state.
Depending upon where the phone is located, the user does not even need to touch the phone -- its state can be verified instantly and by the quickest glance visually if the phone is already in plain sight, needing no reaching & manipulation.
The mute state can be verified by feel, via a quick, light touch of the phone in your pocket. Often I find myself in a situation where I want to enact mute very "stealthily" so as to not distract others in the situation you I'm in (church, a work meeting, an important dinner, or anywhere I don't want to show others I'm taking my attention away from them).
I've adapted to the removed home button on phones & iPads but there are times I miss it; it was a much more reliable method then swiping up, especially for those of us who don't treat our phones like jewelry fashion statements and use cases in the real world.
I would group a physical mute button into the grouping of items that should never go to solid state, and should be readily available for instant use (and not require shuffling thru menu buttons to accomplish): physical keyboard keys on a keyboard, a physical on/off button, volume, and at least one physical jack for power/data.
Apple often forgets that phones/tablets/computers are not design contests. Not everything on a mobile device needs to be simplified down to the most basic, minimalist implementation.