All the underlying physics is the same for everything in this universe so that's not really an enlightening statement. At the level of application it's not exactly the same physics because the approach is different. And you have to understand the approach to see how simple the 70V math is.

With 8 ohm speakers, you have to have loads in the range of 4 to 16 ohms, though most would say it has to be just 8 ohms. Each power amp channel has the same load (more or less).

With a 70V system, the transformer taps are used to choose how much power goes to each speaker and the system will be okay as long as the total power determined this way doesn't exceed the available power.

Both approaches can survive even if very poorly designed, if you simply don't turn up the volume enough to reach the limits of abuse of the amplifiers. That doesn't mean that someone making such a system would understand it, though. This is true for 8 ohm as well as 70 volt systems.

For instance, a studio "sound guy" installed a system in a man's home that had one beefy SAE two-channel amplifier designed for 8 ohm loads. It had six 8 ohm Mortronics volume controls, each feeding a pair of 8 ohm speakers. He accidentally helped this system survive by wiring it with individual pairs of phone wire. The amp lasted almost twenty years before it died.

You can do all sorts of wrong things and have stuff survive if you don't happen to exceed the limits. But that's really another topic.

At some point, trying to use consumer electronics to drive 8 ohm speakers directly will bite you in the ass.