You seem to have misread some parts of that.
The 3/4 and 43:1 ratio was of those who were suspected of not being honest about age during the application process, not of all asylum seekers.
As the article itself already points out:
"The Migration Agency stressed the figures did not show that asylum seekers who lie about their age represent the majority of applicants, as the tests are only carried out in cases where it believes existing evidence is not enough.
"If all unaccompanied minors had undergone a medical age evaluation then the results would likely have been different," Daniel Salehi, a manager at the agency, told Swedish newswire TT. He said the result would then have been the opposite, that most unaccompanied children are indeed under the age of 18.
Over 35,000 asylum applications were made by lone refugee children in Sweden during 2015,
followed by 2199 in 2016."
Now depending on which country they are from its also not a massive leap to be unsure of your age (and the article doesn't say how much older they were - 19 is quite a bit different from 30 for example), take Afghanistan as an example. Not only has it been in semi-constant conflict since 2002, but prior to that was ruled over by the Taliban, who were fairly lax when it came to detailed administrative control.
As such I would be wary of automatically assuming deliberate deceit in every case (some will of course be just that), nor would I say its grounds to automatically send someone back, process them as an adult yes, but an automatic no because someone might get their age wrong by a year?
My own mother in law doesn't know exactly how old she is, she could be 80, 81 or 82. She was born in India at a time when record keeping was pretty poor. Two records of her birth exist in India (found over the last ten years or so by family going back) which date her as either 80 or 82, yet when she arrived in the UK in 1952 her DOB was recorded to put her at 81.
Sometimes its not quite as black and white as many would like it to be, well unless you want to totally remove the human element from things.
