Log axes for highly-variable or compounded-growth data are not only valuable for showing low-scale movements, but greatly reduce apparent growth. They're commonly used in financial data.
For readers from outside the UK, you should understand that the 'authority' here isn't really a government body, and never really issues punishments.
They pretty much embarrass companies into having good honest ads, and mostly it works. No company wants to be called out on having a dishonest ad by them.
Compare:
Linear scale: https://fred.stlouisfed.org/graph/fredgraph.png?g=oMZ6
Log scale: https://fred.stlouisfed.org/graph/fredgraph.png?g=oMZi