In my experience, it is not just restricted to the Mail, since the press seem to think it "open season" on MyTravel at present, due to the disastrous perfomance of certain senior management over the last year or so.
If you are referring to the cost comparison on package v independent holidays, since MyTravel is probably the largest carrier, then it is likely that their figures will be used as a comparison. I was more concerned that this particular report did not consider "like for like", in that the comparison hotels were described as "of similar class" or words to that effect. In one example - La Manga, you would be hard pressed to find a similar hotel to the Hyatt!!
I can actually confirm their findings with respect to a holiday we have just taken in Tenerife over Easter. Booked last August, we got the all-inclusive Bahia Principe for 140Euros a room for a fortnight. We travelled with Iberia, at 175GBP for each return ticket(inc tax etc). We had to pay our own transfers and put up with stopovers in either Barcelona or Madrid on each leg. The cost of this (at 1.4euros/GBP) was 875GBP each. MyTravel, through their Direct subsidiary, wanted nearly 1200GBP each for exactly the same dates and duration!