I am building various contraptions in survival, and I find that I am constantly 'accidentally' breaking slime blocks, e.g. right after mining the block in front of them my pick swings one more time, or I accidentally punch them, or whatever. Very frustrating after you spend a lot of time building a contraption.
It is really annoying to have a 'mechanism' block that breaks the moment you breathe on it. Something like 'piston' has an appropriate breakability hardness/tool for frustration-free mechanism-building. Please make slime blocks take more effort/intention to mine.
Most likely intended.