The phrase "Ever notice that couples that are truly happy" implies that the quote is referring to couples who have a deep and authentic sense of contentment and fulfillment in their relationship.
The quote goes on to say, "never post about it," which implies that these truly happy couples don't feel the need to constantly broadcast their happiness on social media platforms. They are less concerned with showcasing their happiness to the world.
In essence, this quote touches on the idea that genuine happiness in a relationship doesn't depend on external validation or the approval of others. It encourages us to consider that the most meaningful and content relationships are often the ones where happiness is a private, cherished experience between the individuals involved, rather than a public display for others to see.