Building from this: the temporal-trend is one issue I hear expressed (e.g. worry about introducing bias in the estimate of the treatment effect if outcomes for the disease in general improve over time or vary seasonally and the randomization sequence happens to look like you showed here). Another with respect to blocking at each center is that I think many people are concerned that one particularly well- or poorly-performing center may exert undue influence over the results if they have a preponderance assigned to the same treatment, and they are more comfortable with a technique that results in (roughly) equal allocation within each of the centers.
I think you can argue that this is related to our field’s tendency to put a lot of attention on the point estimate and less on the uncertainty.