In January 2017, Bitcoin dropped from 1176$ to 755$ (35%). Today, it's still 10 times higher than last year.
If someone misreads the chart as linear the current drop would be terrifying though, with no previous precedence.
No, it's not designed to hide volatility, it's designed to show a quick overview of the long term changes of Bitcoin. Logarithmic scales are incredibly useful when you have very fast rate of change. Look at a linear chart of Bitcoin over the same range, it's not very useful.
You can quickly see from this chart that Bitcoin is still on a massive tear, though the annotations are a bit cheeky.
The same size drop is always the same % drop, a linear graph would be dishonest