I agree. As an introvert I need a certain amount of time for myself to think and ponder the events in my life and process things as they happen. Without that I begin feeling lost and risk making bad decisions. I think having a strong relationship with yourself is the foundation on which you can then build strong relationships with others.
I don't think we learn to be alone first but who knows what we think of in the womb. Once born, it's all about social interaction. Later we might become introspective. One philosopher said the unconsidered life wasn't worth living but so many people live it and are content enough. One of the Bible prophets spoke of knowledge increasing sorrow - For with much wisdom comes much sorrow; the more knowledge, the more grief" (Ecclesiastes 1:18). Loneliness is now classified by some as a disease. The article probably means voluntary isolation rather than loneliness - a time to recharge batteries and mull over things that need time for reflection. It is probably for the best if we spend less time reflecting than we spend interacting but I'm sure any self-respecting Buddhist would disagree with me.
Like most things, I think it's a matter of balance.