I'm aware of the practice. I'm also aware that there is not total agreement at the parish level about how to use the Orthodox name in convert life. I am communed as Gregory. My family and friends still call me Lee. I am usually referred to as Lee Gregory by many in my parish. Frankly, I don't care.
But I'm still uncomfortable with the dearth of indigenous African (non-Coptic) and East Asian names from which those folks can choose. There has to be a better mechanism to use in order to "open up" new names for converts in these nations.
Some folks might not understand why this matters, but it does. Especially if the Church is trying to make more inroads into counties like Kenya or Japan....an intelligent, culturally proud Kenyan is going to occasionally have some difficulty going by "George" -- and why shouldn't he, given the history of colonialism in the continent?
It's nice you're concerned about the feelings of possible converts to Orthodoxy, but if we all used history and our own cultural background as a standard we could find a reason to all hate each other forever, and never be anywhere close to God. Just ask the Chinese about how intelligent and culturally proud the Japanese are, for instance. Colonialism is a method of wealth extraction for the benefit of the metropole, which still goes on today in various guises. This does not seem to be the Orthodox missionary agenda, and one would hope a person would realize that before they ever got remotely close to converting.
I guess a person has to decide what is more important to them, and as you've stated yourself, they don't have to use their baptismal name for day to day affairs. As far as I know it isn't a Tradition, but people far more holy and knowledgeable than I have said it is a good idea. Some people only use their Baptismal name when they take Communion and Confession. Conversion doesn't require throwing off one's culture, which is probably impossible anyway. It can sanctify and improve that culture though.
Changing names has a long tradition even in Judaism. Years ago I read somewhere there is a belief, I don't know where it comes from, but if you change your name, you change your fate. An elderly Jewish man explained this as he had come close to death, and when he survived, he changed his name, and many of his priorities in life changed as well.
It may help people to leave behind their old way and take up Christ's Way.
Anyway, it seems like it bothers you, and that's the way it is until you decide that other people can make decisions for themselves, and no one is holding a gun to their head to convert and take the name Polyeuctus or Thalelaeus or Audifax or Phileortus.
And who know, maybe they will be moved by God to love their saint and be so happy to bear their name, and try all the more to not sully their good name. With God, all things are possible.