In my early days of playing roulette, I have examened samples of more than 1M spins of the Wiesbadener Spielbank. The results are predictable.It is very easy to figure out the HE for the ECs and Dozens. It is not surprise the results are about 2.7%. The difference between for example between the ECs are often more than 100.
A very big number of difference croupiers has created a 1M sample. It is impossible to find a signature of a croupier.
I agree wheel watching and looking for a bias is waisted time.
When I examine Spielbank Wiesbaden Permanenzen, I use pen and paper. Rather old fashioned, I know. For me it would be a terrible waste of time
to examine more than 1M spins.
You write that "The difference between for example the ECs are often more than 100".
In our heads we might be perfectly balanced. But when it comes to probabilities, the perfect balance sometimes seem to be as deceiving as the socalled signature. Time is most important:
If the difference is 100 right after 500 spins: 20%.
If the difference is 100 right after 1000 spins: 10%