I've done some digging and I'm noticing objectively what feels like the first time the subtle indicators that mark very strong statement as written within the duality description from socionics.com
"These relations are the most favourable and comfortable of all intertype relations providing complete psychological compatibility." - there you have it folks, the two words that stand out are MOST and All. why? Duality relations are the most favourable and comfortable of ALL intertype reltaions. That is a mammoth statement when you really consider that there is sixteen intertype relations. I interpret most favourable to mean successful and comfortable to mean solid.
"They usually understand each others intentions without any need to say a word." I have to emphasize USUALLY, well what does he mean by usually understand each others intentions? Not always or definitely for sure. They can misunderstand each other's intention or sometimes they need to explicity state what they intend. Another matter of interest is a person needs to have a clear intention in order for anyone else to pick up on what they intend. So when one dual partner does not have strong intentions the other partner can not understand. I mean to say there is shades of gray to intentionality. As a rule of thumb the more intent you are the more likely your intention will be understood and the truth is the same for the opposite.
"Conflicts between Duals are very rare and if there are any, they are normally short lived and solved without pain." Maybe its just me but conflict resolution with your dual in theory seems contrary to personal experience. I suppose you could say I've had those very rare experiences.
"Your Dual partner will love you just for what you are and if there is such a thing as true love then it could probably only occur in relations of Duality." - as for the part about 'love you just for what you are' there is alot of things he is not saying. Also notice PROBABLY. That is a tricky word as probably does not mean the same as certainly. Actually the statement sounds a bit weak. There is a 70% probability of rain tomorrow - that does not mean that it is going to rain tomorrow but casts doubt that it is going to be clear. To interpret that another way. If one dual partner is uncertain they want to be with another dual partner than they probably will not be together. Basically he is saying there is a good chance - its a risk, not a guanrantee!
"In fact, younger people have more chance to succeed in the quest for their perfect partner than older people. But the chances are always there." He makes it abdundantly clear that he is talking about CHANCE. Duality is a gamble.
"There are at least two conditions to be completed for a successful relationship between Duals." Did he say conditional? as a matter of interpretation isn't true love suppose to be unconditional? the description is flawed!
"Firstly between the partners there has to be at least a minimal mutual attraction." - true.
"Secondly and most importantly is that the partners are truly striving for the same or similar things. This may include common interests and/or life goals. Partners that are both seriously thinking about building a family are a good example." hmmm these days people are beginning their careers and families later in life when they are not so young which diminishes your chances of finding the perfect partner.
"If relations crumble it normally happens in the first stage." - true. I'm not sure what the stages are and its stupid to mention that they're several stages without actually mentioning what thoes stages really entail. Tease.
"The more stages completed by Duals the more unbreakable their relationship." - I hope so.
"Usually during first contact extroverts think about their introvert Dual as ordinary and simple, therefore not deserving their personal attention." - there is confirmation bias happening on this forum because of this statement. He does say USUALLY during first contact, again, not always, only sometimes, and if any, the first time you meet.
"The magnetic effect of Duality becomes obvious when partners do not see each other for a while." - incredibly true.
"Only after being together for a fair amount of time do the partners start realising how much they need each other." - maybe.
here is a great song. irrelevant to the theory of socionics but seems to fit fine.
"Finally, these relations are most suitable for friendship, marriage and family life." - I have to admit the only time I've ever seriously considered marriage is with a dual but that is personal.