Remembering the last used size could be a workaround, but as far as I can see Core Shell doesn’t do that either (at least not if you close a session using the macOS ‘close window’ control). The other problem is that when re-sizing a window one has no idea what size you are resizing it to (in terms of terminal rows and columns) since, unlike other terminal apps, it doesn’t show the size as the window is being re-sized.
I’m a software engineer and I do most of my work via terminal/SSH sessions to various hosts (mainly Linux but also Solaris, AIX, macOS, …). I may often have 10 or more sessions open concurrently. Depending on the host/task I need a terminal of a specific size so that I can be sure that text based UIs fit correctly. hAving no way to accurately size a window, either when it opens (preferred) or when I re-size it greatly impacts the usability of Core Shell, at least for me.
Though of course this is all irrelevant until the crash is fixed 