Dunno, wish I had his self-confidence.
He retired as a Major in the US Army (he’s also a Colonel in the California State Guard, but that's less of a qualification) after 24 years of infantry service, including two combat tours in Iraq, and he is the chair of urban warfare studies for the Modern War Institute at the US Military Academy (West Point). [0]
So, when it comes to urban warfare, he probably has some idea what he is talking about.
[0] from: https://www.ausa.org/people/maj-john-w-spencer-us-army-retir... except for the State Guard rank.
I was not trying to say he wasn't trustworthy, I am sure he means well. (plus, I am certainly not qualified to judge his advice)
What I am thinking about is this: how confident can you generally be with applying your expertise/giving advice, when you yourself learn about the circumstances from secondary sources? I mean, he's not on the ground, but he confidently describes very specific barricade shapes, etc. If I were a naive protester, I could set up these barricades — and immediately interfere with the regular army, with movement of our own troops, etc.
How do doctors know about diseases they haven't had themselves?
Someone who's experienced one specific conflict, even first hand, may know less than someone who's studied a range of conflicts and derived and war-gamed doctrine from what they saw.
He's literally both a colonel and a professor of urban warfare.
2) That's a massive accomplishment by the armed forces of Ukraine, but it is still useful to advise civilians and make them better prepared in case the fight gets to that point. They weren't handing out assault rifles to civilians for the lulz. I'm sure there are a lot of people among them who have no fighting experience.
I also wish I had self-confidence to say anything that suggests that Ukraine reversed progress of German troops. It was Soviet Union that did that in an offensive which started shortly after the battle of Stalingrad. Ukraine was under Nazi occupation throughout majority of the war with one major nationalist insurgency group fighting both Nazis and Soviets simultaneously.