Hi blades -
They certainly do - supply and demand. The skew can be enough to make a big difference from the TA you will see on the real chart and the TA you will see on the SB company's tick charts e.g. real FTSE100 might show a clear S/R level due to repeated tests and retracements: whereas the tick chart could have been all over the place on the same occasions, masking the real S/R level. The tick charts are also not reliable for use swing trading methodology triggered by breach of high or low of a swing day - the tick chart might not show the breach at all, or show breaches on another day.
In general Rolling or Daily Cash quotes are very near the underlying instrument, quotes for March, June etc. will be more skewed.
I suppose there might be a way to play the skew against the SB companies if they get the direction wrong, shorting high when they skew higher than the market, which then falls, and buying low when they skew lower, and the market then rises: I have a feeling this is a theoretical opportunity, not a tradable one but mabe some other users have worked out a system?
Note that the spread also widens outside real market hours.