I haven't taught algebra to 8 year old kids, so maybe if those methods work they're ok. I have to say I'm skeptical though, why not hold off until they can do with a method they will still use find useful as adults (or do many adults still use bars in everyday life?). There must be easier problems they can do before that that don't require bars. My own personal experience is that I found word problems really, really hard to do until my elementary school teacher taught me algebra.Do you teach algebra to 8 year-olds? If you do, then I want to learn your secrets.
This IS teaching them algebra. It just takes a little time to transition from concrete examples (blocks) to abstract reasoning (x). There are other ways of teaching algebraic concepts to young children, but they almost all use something concrete as a bridge to 'doing it right.'
We could ask this: Why don't we just teach primary school kids about fields and rings? Well, in fact we are - using ideas that they understand and building up to more abstraction as they have enough experience to make sense of it all.