montreal-
I agree with you 100% regarding Spanish spoken in Argentina. In general terms it's very good Spanish grammatically, phonetically different because of the /zh/ and lexically (vocabulary) different sometimes but that is not exclusive to Argentina. In Spanish in general word variety is very extensive and in many cases simply looking in a dictionary to find a word is difficult because of the choice. The standard word vs. the regional word vs. sometimes a more specific lexicon that is used in certain scenarios can leave you puzzled. One aspect you will note is that word choice in Argentina is similar to other countries in the R?o de la Plata region aka the southern cone which includes Uruguay, Paraguay and Chile. One other aspect you have to take into consideration is that Argentina has a very large population (over thirty-five million), more than one linguistic zone within country, therefore it is inevitable that vocabulary will vary within the country and as compared to other Spanish-speaking ones.
The examples you gave are of fruits so that's normal in Spanish to have variations however, anan? IMO is very specific to that region. In Latin America you will not hear anan? out of the blue. The standard word is pi?a. I would also say that many Spanish speakers probably have never even heard the word. However, I see this as typical example of word choice associated with the region. As you and I know in French ananas= pineapple (even in Quebec) therefore, possibly the European influence in that region is a result of the word choice in Spanish in Argentina.
Let us know what you find out regarding the /j/ and /zh/ for your own curiosity. I am quite sure it's a phonetic feature of Spanish spoken in Buenos Aires. If you have the opportunity to speak to some old school Argentineans about Spanish most will say that Spanish in Argentina and South America in general is changing for the worse and my response to them is always, it's not as bad as the Caribbean or Spanish spoken in the USA. Location may play a role in this in that Argentina is so far removed from other Spanish-speaking countries that have inevitably been influenced by English and other social dynamics as they relate to language.
BTW- Argentinian or Argentinean are both accepted orthographical forms of the adjective.
Chao
-LDG.