Joseph, that is not accurate. Most Chasidim do not go out at 17 years of age ( actually most Chassidim do not go out at all- we have beshows). We started listening to shidduchim for my son when he was 19 and he got married by 20. My 19 year old daughter just started shidduchim, most of the boy’s that are read are alproximately 20 years of age. We are a regular Chassidishe family listening to regular Chassidishe boys. My daughter has only 4 engaged girls out of her class of 30. She attended a very Chassidishe school.
Even Satmer boys who get engaged young are generally at least 18 years of age while there could be kallahs 17 years of age but they wait until they are 18 to get married and they are a minority. Most boys and girls in the very frum Chassidishe crowd are at least 18 when they start listening. I do know of a Rebbishe girl who got engaged at 16 and married at 17. But even for Rebbishe, it is very young. My friend has an 18 year old son in Satmer yeshiva and none of his classmates are engaged yet.
The trend is certainly not 17 years of age. In Israel 17 years of age is also not the norm. Maybe by the Meah Shaerim Chassidishe like Reb Aharon’s Chassidim, maybe they go at that age. I’m not familiar with that shidduchim scene.