FINALLY! Very welcome - and also - I'd say - about as unlikely to be a random decision Inno's made as this alteration's silent introduction would indicate (although, had this change actually been overtly pointed out to us or anyone else, I'd assume it was, whether wholly or partially, an attempt to promote the fact that some expiring buildings rarely give out small sums of Diamonds - as some players still aren't aware).
In fact, I would take a small bet that this has happened for no other reason than the interesting (and also under-reported) fact I've just myself become aware of - namely the recent news that in at least some European countries, video games which are either wholly or even in part reliant upon gambling are now legally obliged to refer to their games no longer as merely 'games', but as 'gambling games'.
And while I've no idea whether this is EU-wide or nation-specific at the moment, nor yet whether Germany is or isn't affected [yet?], from what I know about law in general, I'd say that the overall descriptive titles of video games won't be the only provision of this new law - after all, when politicians finally introduce any type of consumer protection legislation, they usually do as thorough a job as they can, if only to save themselves time and complaints from their voters the public. As such, it seems probable that, somewhere down the line, it's necessity (present or anticipated) which is causing Inno/MTG, and other gaming companies too, one assumes, to prominently show what was formerly often hidden from all but data-miners, i.e. the actual % reward chances of ANY building/item [with RNG-based rewards] which may involve cash expenditure in obtaining it, whether or not there's the argument that some, or even all, players can alternatively also obtain said item(s) without spending (ref. the frequent debate on the extent to which Event and similar RNG-based rewards are/are not attainable via payment of some kind vs via grinding/luck).
Taking the chance of being proved wrong here, of course, but still, I'm pretty confident that we'll see this kind of info now appearing on all similar buildings in future (and with retrospective effect, too, most likely - with Genies being, of course, the most obvious candidate there).