I dunno [Edit for Zealous mods “dunno” is a phonetic way of saying "Don’t know - it is not "Gibberish 
] - We used to get spreads running away in front of sudden price changes in the old spread betting days too. They sort of widened in proportion to the emotional pressure the movement was inflicting ! TBH I don’t blame them for that - It just seems logical if you’re taking the reverse side of the bets.
In fact, whatever you call it, without level 2 direct access any system with a gap between Bid and Ask - is just that- “Spread betting” - except these people actually add interest to overnight positions, despite them being pure “Bets” . - The other thing is that in the UK at any rate “Spread betting” does not attract tax = probably because it would end up being a tax-negative situation from HMRC viewpoint.
This “Trading” - I believe does mean paying tax, although to hit “Capital gains” limits would make you a specially gifted person !