For some reason, the desktop site migrated to using sblock tags, and spoiler tags did nothing. Meanwhile, in the app, sblock tags did nothing and only spoiler tags worked.
This meant that you either
a) ignored or was unaware of the app, and just used sblock tags. App users got their day spoiled. Now you must change everything.
b) applied both sblock and spoiler tags so that one or the other tag protected your content, regardless of how the thread was read. This means you should be fine: even if non-functional sblock tags will still litter your threads, at least the spoiler tags (that previously only worked in the app) now start to protect your spoilers for everyone
tl;dr: everything was worse before but is better now