While I'd like to agree with you that if this looks like trade and quacks like a trade then it's probably a trade (or whatever that saying is) the caselaw tends to disagree.
Manzur is probably the most recent case and suggest that in order to turn currency trading (or stocks and shares) into a trade there needs to be a very high level of activity (he was 'only' 240-300 transactions a year), organisation, professionalism (ie a former trader undertaking his former profession in a personal capacity), providing services to clients and hedging of risks.
Crypto may tick these boxes, but Manzur was pretty active and still deemed to not be a trade.
HMRC do give some specific guidance in this
https://www.gov.uk/government/publicati ... currencies but it's not really much help.
My view is generally they want to avoid calling people trading as they can then offset losses against other income.