He chose Boris over Alexander? Wow!
So many first names have common spelling variations that people need to spell them out, regardless how well-known the name might be. I've known some of each of the following:
Linda - Lynda - Lynnda
John - Jon
Mark- Marc
Neil - Neal
Jenifer - Jennifer
Carol - Carole
Karen - Caren
Hanna - Hannah
Sara - Sarah
Stephanie - Stefanie
Erma - Irma
Jerold - Gerald
Katherine - Katharine - Catherine
Steven - Stephen
Kristine - Christine - Khristine - Cristine (same variations but with an A at the end)
Derrick - Derek
Garrett - Garett - Gerit - Garret
Nicholas - Nicolas - Nickolas
Debra - Deborah
And so on.
As a few on this forum know, my real name isn't unheard of as a name - though it's never in the top 100. However, it's a well known word that's only four letters. Even so, I typically have to spell it out because it's a common Asian name, but with the final letter dropped.