I have never heard anyone using the term Aryan invasion theory for any Indo-European culture except for India.
I am baffled.
Why should that matter?
Are we concerned with the sequence of events or what they were called?
Indian population have ancestry from two sets of races called Ancestral North Indians(ANI) which are Eurasian related to people outside India and entirely native Indian races called Ancestral South Indians(ASI) related to no one outside South Asia.
It is a common mistake to think that either was a pure race; these are genetic types, which were not existent in 'pure' form at any time. In fact, geneticists agree that there was an outward migration from India sometime around 30,000 BC and that since then, until the ANI/ASI juxtaposition, there was no change in the genetic composition of Indians.
The purest ASI stock is among the Andamanese Islanders, and there is not a single other case of undiluted ASI genetic composition.
There was and is no pure ANI stock. All the ANI genetic components came into the geography already partly diluted.
The two races kept on mixing from 4200-1900 years ago until there is origin of endogamy(marriage within same caste) around 1900 years ago. The genetic studies was done on 74 castes of India by Harvard Medical School and CSIR-Hyderabad.
The South Indians in general have 40-55% of ANI ancestry including low caste Hindus in South. Even the remote tribes and nomadic communities have this ANI ancestry. Same way all North Indian have high percentage of ASI ancestry ranging from 35-60%. Now, such genetic test puts a big question mark on the garbage that came attacked with Aryan invasion theory.
Why so? This just points to very deep and thorough admixture between 4200 years to 1900 years ago, which is what I presume is what you mean. That is an admixture through two thousand three hundred years. What isolation of genetic characteristics do you realistically expect to see after that long a period of free contact and socialisation?
You can read the links I posted, that's a good site of reputed archaeologists, it will tell what existed between Indus Valley civilization and Vedic culture.
Cemetery H culture(1900-1300BC) also called Ochre coloured Pottery phase matches with Rigvedic geography of Sapta Sindhu(purple in the map) and there is also strong signs of early Hinduism. The culture is named as cemetery H culture because of the proofs of cremation in Harappa in Cemetery H region. After Indus valley civilization's last phase there was migration of people into more fertile Gangetic plains from semi-arid Indus valley plains where they were able to cultivate Kharif crops instead of barley.
This one Late Indus Valley civilization divided into three disconnected regions Cemetery H(purple), Jhukar(yellow) and Rangpur(red)
What happened after 1800 BCE? | Harappa
Once again, I repeat: these are surmises, very intelligent and very instinctively appealing surmises, but surmises nevertheless. They are not proven, just as the immigration of Indo-Aryan speakers is not proven.
I happen to think that they are right on the ball as far as the fate of the descendants of the dwellers in the IVC are concerned, but not as far as forming a single point of development for later India. These are intelligent reconstructions of the diaspora from the IVC, but that does not mean that I consider them to be firm, established fact. They are not historically valid. And, most of all, they do not indicate that there was no linguist injection of a new language, probably introduced by external speakers of that language.