I’m probably dating myself but does anyone recall when then Chief Justice William Rehnquist was concerned that some court observers might not be aware that he was the “gadol among gadolim” and used a fashion statement adding a black velvet collar and four gold stripes on each arm of his black robes. He later protested that the sartorial statement was less a reflection of his insecurity and simply a whimsical emulation of the Lord Chancellor in his favorite Gilbert and Sullivan opera “Iolanthe”.
Perhaps the velvet collars you see on some kapotes are simply a manifestation of an inner yearning among the Litvish to share in the fashion statements available to their chassidishe brethren and distinguish themselves in a sea of black hats w/o being too obvious and raising an issue of tzinius through a visually jarring change in uniform. We all know that behind many ltivish is a chassidish waanabee.