Precisely.
Augusta is closer in sound to names such as
Isabella,
Olivia,
Arabella, etc. And
Augustus is increasing in use for boys.
But most of it is the difference in age.
Augusta's previous period of popularity came definitely before
Winifred,
Muriel, and
Roberta, at least in the USA. There were still a lot of Winifreds and Muriels being born in the 1920s; by that time
Augusta had practically disappeared as a name. And
Roberta is even "younger", peaking in use around 1940. So, ironically, young parents today think of
Winifred,
Muriel, and
Roberta as still being "ugly" because they know real elderly women who have these names. Very few young Americans today know an
Augusta personally; almost all the
Augustas of the past were dead before they could remember them as real people. Ironically, that's what makes the name sound "fresh" and "revivable" to younger people. If you can't remember the association between the name and gray hair & wrinkles, it can turn in its image from "old, ugly, and outdated" to "retro, old-fashioned, and cool". :)