The bottom part of the forever block has a line at the top that goes through the celebrate block. This also happens with the flat design.
That looks like the celebrate block is just slightly transparent, in fact, it just looks like you have the "fade blocks" setting not set to 0, because I don't see that line on my device, only if I set fade blocks to 10 I can see it.
Stupid me, you are right. I experimented so much that I forgot about this one. 