ACR 12.3 is not suitable for users with large numbers of images.

https://feedback.photoshop.com/photoshop_family/topics/camera-raw-12-3-how-to-revert-ui-to-older-version-one-with-vertical-filmstrip?topic-reply-list[settings][filter_by]=all&topic-reply-list[settings][reply_id]=20598203#reply_20598203

The crop tool reverts to 'full frame' so to speak.

There's a number of ways to save the crop in ACR (or LR), depending on what you want. You can do a "Copy Settings" and then "Paste Settings: if you have a number of images selected. This can be done from the filmstrip clicking on the three little dots. You can still save a custom crop at that ratio but you'll need to select it for one image, then again, copy and paste to all others selected in the filmstrip. 

You can also do a "Save Settings" as a Preset and call it up at any time using a similar GUI. If you only wanted the Crop, you'd probably select first "None" then just click on the "Crop" check box, give the preset a name then recall it whenever you wanted it. You can even save this out as XMP to load but a preset is probably better (XMP would be useful for saving across multiple computers). 

With the Preset, you could have just this crop but you could have a crop and any of the other settings built there too as seen below where I have crop and geometry in one preset.