請益，有關A7系列的暗部對焦

以下數據都是查官網的
A7 : EV 0 to EV 20 (ISO 100 equivalent with F2.8 lens attached)
A7II : EV-1 to EV 20 (ISO 100 equivalent with F2.0 lens attached)

A7S : EV-4 to EV 20 (ISO 100 equivalent with F2.0 lens attached)
ASSII: EV-4 to EV 20 (ISO 100 equivalent with F2.0 lens attached)

A7R : EV 0 to EV 20 (ISO 100 equivalent with F2.8 lens attached)
A7RII: EV-2 to EV 20 (ISO 100 equivalent with F2.0 lens attached)

怎麼一下F2.0一下F2.8的?

所以A7II其實根本沒進步?

兩代A7S其實都只有-3EV?

A7RII其實只有-1EV?

可以這樣解讀嗎?