Anyone have any idea what cable is this

Splice connectors such as US-style wirenuts and UK style terminal blocks are demonstrably better in nearly every way to the twist-and-tape method you describe.

1. Wirenuts and terminal blocks are more resistant to mechanical failure due to heating/cooling cycles and the mechanical stress of installation.
2. Wirenuts and terminal blocks are easier to inspect and test, even long after initial installation.
3. Wirenuts and terminal blocks are easier to install CORRECTLY and require less training to do so.
4. Wirenuts and terminal blocks can be quickly removed, and can be re-used without shortening the wire.
   1. Tape can be removed and the wires reused, but the process is labor intensive and messy because of the adhesive. It's easier to cut the wires before the splice, thereby shortening the wires.

So why are wirenuts not more common everywhere? Cultural bias and intertia. For example, wirenuts are not commonly used in the UK because an early wirenut product in the UK market had a design flaw and frequently failed, spoiling the reputation of the product. Terminal blocks became the standard by default. Because of this history, wirenuts are seen as inferior in the UK, when they are empirically not. They are just different than the commonly used terminal block.

I would argue the same is true for twist-and-tape joints in Brazil: it's how it was done in the past, and anything different is strange and therefore must be wrong. The only difference is that, at least for household wiring, wirenuts and terminal block are empirically superior to twist-and-tape splices.

Yes, because a poor connection due to subsequent corrosion can affect the signal which may well cause unreliable operation.

There are waterproof junction boxes available which you should use.