I couldn't be bothered to watch the full 30 min video, so here's just a few notes, based on the few scenes I watched:
USB3.0(A) is specified to provide 0.9Amps of power. For the standard 5V power that translates to 5V * 0.9A = 4.5W. There's a higher limit of 5V * 1.5A = 7.5W, if the port is designed according to the Battery Charging spec, but I don't know whether that applies to the ports in the Mac mini and will thus only consider the lower value below.
Thunderbolt 3 is specified to deliver up to 15W for a connected device. So if the hub is connected to both a TB3 and a USB3.0 port, itself and all connected devices together can theoretically consume 19.5W (even though it is considered bad design to connect to two separate USB ports for increased power supply - but technically it's possible). On hubs with a single TB3 connection, the power limit would be 15W respectively.
The 2018 Mac mini's PSU is rated for 150W.
According to Apple it can consume up to 122W under load. My understanding it that this is without externally connected devices. That leaves 28W to spare, which would be sufficient for the formerly mentioned 19.5W (15W) for the Hub and its devices.
On the other hand, with components aging over time (especially in a crammed and heated case like the Intel mini), tolerances may add up in an unfortunate way, so the reserves may shrink!
According to
this site a single SSD can consume up to 10 Watts during sequential writes (PCIe SSD's even more, but those don't apply here). Sequential transfers are not the norm and rarely sustained for longer periods of time, but I'd rather look at the worst case here to err on the safe side.
If you would connect multiple SSD's (or even platter drives) to the internal and external ports of such a hub and load them all at the same time, you may quickly exceed the given power limit.
The Hub suppliers do make a little gamble here, relying on most customers not connecting all available ports at once and putting load on all connected devices at the same time. Probably there's also something in the fine print about maximum connected/loaded devices as "cover-your-a$$" fallback.
If you approach this with reason and sum up the power draw of connected devices, you can make sure to not overload the system.
I'm not so sure about the video guy's recommendation of using a dedicated external PSU for powering the hub. In theory it sounds good, but I would be careful with providing power to a device from two separate sources (mini's PSU and external wall-plug PSU), as that could bring other unwanted negative effects.
tl;dr: Depending on workflow and connected devices on the hub - yes, there's a chance to actually overload the system under certain circumstances. In practice, the stars would have to align in a very negative way for that to happen.