[DCP-o-matic] Scale to fit width/Scale to fit height

Hi everyone, wondering who is using the Scale to fit width/Scale to fit height feature on a regular basis, or so to say, intentionally? I thought about these options very often now (probably too often), and I can't get a grip on it. In my work with DCP-o-matic, I never saw a need to use it. I thought I could get a better idea if I'd just play around with it, but it doesn't seem to react in a way that allows me to see through. E.g., when I select content and then choose either option, it applies a change to scaling/cropping once, but then doesn't revert back if I choose the other option. In my current trial, it presets a crop factor, I can reset that manually, yes. But it uses the same crop values for both Scale to fit width AND height? Initially I thought these options would express the implementation of non-standard-aspect rations in the sense of the DCI/SMPTE standards: One or both dimensions of a custom size container always needs to be the same as a full container - e.g. either vertical 1080 or horizontal 2048 (or their 4k counterparts). But that doesn't seem to be the case? Is it just a shortcut to two prominent scaling options? Do these options still make sense since DOM is choosing default scaling for content based on content aspect ratio for a good while now? The reason I am so picky about this is, I'm doing the german translation, and I have a hard time finding a good translation if I don't understand it... Anyone? - Carsten