I will still say that lacking the ability to communicate via a particular medium is not the same as lacking social skills. My inability to send messages via Morse code over telegraph lines doesn't mean that I lack social skills.
Likewise, your parents certainly don't have any problem conceptually understanding keyboards, letters, or addresses - they were perfectly comfortable with typewriters, letterheads, and postal codes. Dealing with nigerian princes and chain mail might involve the use of technology, but these are very much social skills.
As someone who only uses social media platforms that are mildly reskinned versions of 80s/90s message forums, I don't really know what the "BCC vs CC" of tiktok is, nor do I care. I have an excellent understanding of how tiktok works technologically, but I lack the particular social skills tiktok requires. Since my peers do not get it either, this has never been a problem for me, but I'm sure in a few years when my kids expect me to just know how to snapple into the televoid with them that I'll look like an idiot as I search for a reply button somehwere.
To your point, if a telegraph operator handed me a message I didn't understand, I could just say, "Hey, I don't understand this message. Can you explain it to me?" because that is social skills.
That I can have someone translate to and from Urdu for me does not mean I have the social skill required to communicate via Urdu. Likewise, that your parents can ask you whether something is spam or not doesn't mean they have the social skill required to communicate via email.
Wikipedia defines social skills as:
"A social skill is any competence facilitating interaction and communication with others where social rules and relations are created, communicated, and changed in verbal and nonverbal ways."
If the ability to effectively communicate via a medium doesn't satisfy that definition, what does? You are welcome to use a different definition, but that's what I am referring to by social skills.
Whether using your definition or another, my point still stands that social media does not lead to GREATER social skills than previous generations possessed.
Not being skilled in ALL aspects of socialization isn't the same thing as lacking social skills in general.
I never claimed that social media leads to objectively greater social skills, there's no reason why being able to write a great email is inherently superior to being able to write a great telegraph message. However, one skill is undeniably more useful in this day and age. It does not matter if you call it a social skill or a technological skill, the fact remains that there are people who know how to communicate effectively via social media, and those who don't, and just because you are comfortable in the latter category does not mean your daughter will be too.