According to you? I've discussed challenges to STR dating,
here and elsewhere.
One thing is clear about Finnish I1 (I1d3), and that's that it is uniform and hence young. It is also apparently shared mainly by people on the Eastern part of Sweden. Since the diversity pattern is clearly Sweden->Finland, we can agree that it went from Sweden to Finland, but Finnish-type I1 isn't seen at the same levels anywhere else. That means that present distributions can't be explained by migration proportions alone, they must be combined with genetic expansions within the Finnish population.
That is to say, Finnish I1 is not clearly non-Germanic, based on what we know right now.
I disagree with your logic.
I1 in Scandinavia is most likely a element of a early time when Ugric-Balto-Slavic populations were much father west than the Finnic-Ugric-Balt-Slavic populations we see or recognize today in the Baltic states, Finland, and north Russia. Everywhere I1 exists it is joined by R1a-M17, which offers a major clue to its origins.
The Svearish Ugric-Balto-Slavic element in central scandinavia was subordinate in tech and exploration for a long time to the militarily dominant Geats-Goths to their south, as the centuries pass and the culture and structure of the Geats are assumed by the Svears (I1).
As the Geats begin to decine in power due to losses in warfare and/or manpower the I1 Svears who are originally likely a Ugric/Balto-Slavic population, rise to power and take control of the Scandinavian continent and the Geatish population who does not flee.
I think you will find a component of I1 that is SNP differentiated and predates the Conquest of Finnmark by Sweden, as well as common Swedish I1 that are residue of the conquest of Finnmark and its aftermath. What you find almost zero of is R1b,
since the Goths-Geats were vassals already conquered in scandinavia by the Svears and not offered a co-equal status in Svearish conquest of the lands to the east.
There is no DNA evidence beyond the early fabrications Nordtvedt wove to guard flanks of his theories that insist this I1 was part of early continental germanic tribal groups. It is obvious without question that I1 is overwhelmingly 'Svearish', and most likely I1 orignated as a probably Northern Ugric-Balto-Slavic group.
The I1 you see amongst 'germanic' populations today is a result migrations from well-known population explosion and migration from Scandinavia into Northern Europe, at the same time of large depopulation of northern euro lands along with other regions of europe at the onset of the dark ages.
There is nothing tribally 'germanic' about I1 no matter how many nonsense early-tribal names Ken uses to attach to a I1 or R1b SNP/Str set.
No I1 is found in pre-dark ages samples on the continent because it was not a component of these germanic populations until the (probably Ugric-balto-slavic) Svear descended populations start to migrate into europe starting around 700-800 A.D. for historically well-known reasons and well document movements.
200 years ago, almost no males in Arizona or California had a R1b Y-line. Today, only 200 years later, most males in those places are R1b Y-line, so assuming I1 is 'germanic' in any way, when it is not even found amongst early germanic population samples, is like assuming a R1b-m269 californian is probably of Apache male descent.
A matter of only a few decades or centuries is of extreme import. At colonization of California, R1b males had a distinct advantage, just as at the onset of the dark ages, for specific reasons, the masses of Svear-descended landless males leaving scandinavia for the lands of the northern continent of europe had advantages to their colonization efforts that begin rather late in european history.