This would seem to support that view, although it's not carved in stone. We just don't know for sure yet: that's why the authors said "MAY".
"The latter group may have been local to the Balaton environs, based on bioavailable reference data from the region."
(The latter group was the southern group.)
Sorry, I left out some important and clarifying information from the Supplement:
"Pannonia hadfallen first under Hunnic, then under Ostrogothic control, when the Ostrogoths movedinto the Balkans in 473. Soon after, in 476, Odoacer, a Roman commander of barbarianorigin in Italy who led a mixed army of Heruli, Rugii and others, overthrew the last WestRoman emperor and ruled Italy as king and patricius by arrangement with the EastRoman emperor in Constantinople. He exerted loose control over the former Romanprovinces to the north and east including Pannonia.
The population of the region thuspresumably comprised descendants of Roman provincials as well as members of thevarious barbarian populations that had entered the region over the previous twocenturies2–4."
The length of stay by the Langobards in Szabo was only one generation.
"The small population settled for only one14generation in Pannonia at the shore of Lake Balaton and therefore appears to have beenvery mobile - especially the women indicate isotopically and genetically heterogeneousbackgrounds"
Also, "Most of the Longobard-period burial grounds in Pannonia are located nearformer Roman villas, forts and camps, and the Szólád cemetery seems not to be anexception, since there are hints of a Roman villa nearby."
As to how and why and when they got to Pannonia:
"in 535 the Byzantine (East Roman Empire)invaded Italy and began a reconquest under Emperor Justinian I. From around this time,Byzantine diplomacy began to develop treaties with the Longobards in order to isolatethe Ostrogoths and to counter the Gepids, another barbarian people along the Danube and3Tisa Rivers, and granted them the “city of Noricum and the fortifications in Pannonia aswell as other towns and a great amount of money”."
"Seventh-century sources attribute the Longobard invasion of Italy in 568 toan invitation issued to the Longobard King Alboin by the Roman commander Narses,although this is not mentioned in sixth-century sources and is greeted with skepticism bymodern scholars2, p. 98-100). It was clear that the battered infrastructure in Pannonia4could not meet the ambitions of a growing Longobard army."
From that it doesn't seem that they spent more than about a generation in Pannonia as a whole, i.e 535 to 568.
"The invasion met with surprisingly little organizedRoman resistance, but still the Longobard conquest of parts of Italy was a poorlyorganized and long-drawn out affair. The main army moved westward and took Pavia,which would later become the Longobard capital, after a siege, but did not move on toattack Ravenna or Rome. Instead, Alboin’s army began to fall apart into separate bandsled by individual dukes who went their own ways, some into southern Italy and othersinto Burgundy, and some straight into Roman service."
"c Paul the Deacon wrote a much fuller history of the Longobards7, drawing on theOrigo Gentis Langobardorum, the now-lost history of Secundus, and otherseventh-century sources. His account, although written over two centuries or more afterthe events it recounts, has nevertheless been taken,
often uncritically, as a reliableaccount of Longobard history, a position increasingly disputed8,9. Concerning theinvasion of Italy, he states that Alboin’s invading army included not only Longobards butGepids, Bulgars, Sarmatians, Pannonians, Suevi, Noricans, and others6,10."
Emphasis mine.