Beginner improvements for room acoustics; very helpful Darko video on reverb and RT60

Yes, he glossed over distance and yes, he gives me the heebie jeebies. 

In most small domestic rooms it's not that big of a deal. Darko is not someone to go to for acoustic advice or really any advice IMO. If you're doing HT in a dedicated room it's a good idea because it can help get better sound field over more seats.  I've done some measurements using REW for interest only.

REW

RT60 is a measure of how long sound takes to decay by 60 dB in a space that has a diffuse soundfield, meaning a room large enough that reflections from the source reach the mic from all directions at the same level. Domestic rooms are usually too small to have anything approaching a diffuse field at low frequencies as their behaviour in that region is dominated by modal resonances. As a result RT60 is typically not meaningful in such rooms below a few hundred Hz. Use the RT60 Decay, waterfall, spectrogram and Decay plots to examine the decay of low frequencies in domestically-sized rooms.

I don't think he's untrustworthy just in it for money which is fine but I take these  YouTube  guys that have a vested monetary interest with a grain of salt. the video you posted has some good advice and some lousy advice. For example when he says you can't get exceptional sound in a normal living space without room treatment from ANY speaker that's nonsense. Cardioid speakers can work very well in untreated rooms.  Wall to wall carpet with thick pad is good floor treatment. Speaker directivity and listening distance is equally important. Is a dedicated listening space optimized better? Well yes but very few people can have that. 

There is no " one size fits all". My biggest problem with peddlers like Darko is convincing people he has the answers when he simply repeats the same old tropes. Absorb, diffuse or reflect first point? Depends. Ceiling or floor bounce good or bad? Depends. All rooms are different, all listeners are different, types of speakers matter, listening distance matters, hearing ability matters, preference matters, most of all the recording matters. Read Floyd Toole, here's an article better yet read his book. 

Since when does preference matter with you measurement types?

Preference is  always important ,  unsupported claims not,  just admit it's preference not a miraculous suspension of physics.