Quite agree, SFFP, but the cloud in that particular picture would not cause more than a moment's thought at any speed, 140kts, 420kts or 540kts.
Before one of the gainsayers points it out, of course we all recognise that the weather 'they' experienced was not as 'nice' as in that picture, but the learning points remain.
What is so odd is the the R O's, who were 'low-level' experienced, should come to such a bizarre conclusion on in-flight conditions with no supporting evidence. On second thoughts, perhaps it really is 'not so odd'?