AND said disc-shaped craft have been dismissed as hopelessly impractical, which leaves you wondering why beings capable of crossing interstellar distances make spacecraft which suck so badly in atmosphere, given that a degree of atmospheric flight appears to be part of the mission profile!
Okay, so perhaps there's something we're missing. Who knows, maybe for a miraculous supraluminal drive, a disc shape is necessary, and maybe this requirement outweights the potential problems of a spacecraft that's inherently unstable in atmosphere. Or maybe their antigravity/drag mitigation technology is sufficiently effective that there's practically no risk of a failure[1].
Or maybe disc-shaped spacecraft are products of delusional minds coupled with too many 1950s Science Fiction movies. . .
[1] If there is ANY failure, the spacecraft would be lost in atmosphere, so this is by no means a trivial point!