Is "The Vision of Escaflowne" a shojo anime?
Yes, The Vision of Escaflowne anime is actually a shojo anime.
According to Japanese Wikipedia, the original draft of the anime was to mix robot anime with elements from shojo manga and transforming military vehicles with the title 「空中騎行戦記」(Kuchuu Kikou Senki, lit. Mid-air Trail Riding War Chronicle)
However, when the anime was localized for the TV broadcast in the USA, it was heavily edited. According to the Wikipedia,

[...]. In August 2000, Fox Kids began broadcasting the series in the United States. Produced by Saban Entertainment under license by Bandai Entertainment, these dubbed episodes were heavily edited to remove footage, add new &quot;flashback&quot; sequences to remind the audience of the events that just occurred, and to heavily downplay the role of Hitomi in the series. The first episode was skipped altogether, and the series soundtrack produced by Yoko Kanno was partially replaced with more techno rearrangements by Inon Zur. This modified version of the series was canceled after ten episodes due to &quot;low ratings&quot;. Fox explained that they edited to meet their own target audience, to comply with broadcast standards, and to fit the allowed timeslot. [...]
(Emphasis added)