The lines are BS for starters, and you are spot on about currency valuation. The USD is signficantly weaker today compared to a year ago.
Long term DOW charts are another pet peeve. The companies in the DOW are totally different today than 20 years ago so comparing values from years ago and drawing trend lines is silly. Add in the currency and it gets really stupid.
It would be the same as having a 20 year chart of the values of cars where you replace any car that goes over 5 years old with a new one.