Let's start with a thought experiment.

Supposing I tell you that zscore(trend, 50) equals 1.2, what can you tell me about the current value of trend?

Is trend positive?

You can't tell because zscore re-centers trend around it's 50 bar mean.

So what can you tell me about trend?

The only things you can tell me are 1. that its current value is above its 50 bar mean value, and 2. that its current value is further from the 50 bar mean than most of the other 50 values.

Conclusion

Some important information has been lost, namely, the sign of the original value. Normalizing data values is often necessary in order to use many data analysis techniques. But for indicator values whose sign is informative, it seems sensible to normalize them by rescaling the values WITHOUT re-centering them.

What do you guys think?