Could it be that the Portuguese wanted to apply their Law as relates to the number of DNA markers which constitute a match and this was unacceptable to the UK whose baseline is 20 markers for a match under the Law?
No, John. The number of alleles examined by the different countries' forensic services is not the issue here.
In that boot sample, they found 15 alleles matching hers in a soup of 37 belonging to between 3 and 5 people in a hire car used by her immediate family, various relations and other people.
Those alleles are not exclusive to her - she inherited them from her parents, after all. A number of them will also match those in her siblings' profiles. And it is quite common to share 5-6 with a total stranger.
The issue is that, because the sample was a soup to which several people had contributed, there is no way of telling whether those 15 were actually hers or were simply the combination of those that she shares with each of the other people who contributed to that sample.
As Debunker pointed out, the initial PT police team didn't seem to understand the soup issue for some reason. Even if there had been all 19 present, the situation would still be the same.