I noticed that if I put a quarter and a whole note in 4/4 time, the whole still fit inside the measure. That was unexpected. I understand it would get placed because I'm not in "Limit to one bar" edit mode, but not so that it appears to have 5 beats in a 4/4 measure.
What I expected was that the whole would get split into a tied dotted-half + a quarter in the next measure.
Poking around, I found out it was the bar option "Don't split notes" that was doing it. Then, I realized I couldn't just select all the bars and toggle off "don't split notes". Instead, it only did it for the one I actually right-clicked.
So, my suggestion is to allow multiple bars to be selected and then changes to "Don't split notes" to apply to all selected bars. Just like changing bar widths and margins applies to all selected bars.