Xamarin Forms 1.5.1 : Android Target 23 Required ?

Hello,

I updated my project yesterday to use the 1.5.1 version to have the support of app compat libraries. I saw that I have to change the target framework/version to API level 23 (Android 6). Is it required ? When I tried to lower it at 22 or 21 I got those compilation errors :

Resources/Resource.designer.cs(394,116): error CS0117: XXXX.Droid.Resource.Color' does not contain a definition for abc_color_highlight_material'
        Resources/Resource.designer.cs(2605,24): (Location of the symbol related to previous error)
Resources/Resource.designer.cs(594,125): error CS0117: XXXX.Droid.Resource.Drawable' does not contain a definition for abc_control_background_material'
        Resources/Resource.designer.cs(3279,24): (Location of the symbol related to previous error)
Resources/Resource.designer.cs(909,112): error CS0117: XXXX.Droid.Resource.Style' does not contain a definition for Base_V22_Theme_AppCompat'
        Resources/Resource.designer.cs(4796,24): (Location of the symbol related to previous error)

I'm trying to lower the target because of this problem :
https://forums.xamarin.com/discussion/44977/listview-scrolling-problem-on-android-m#latest