When placing piston (sticky or normal) upwards with redstone block on top and powering it the piston will stay extended after beeing depowered. Updating the piston or redstone block does not make it retract When the top redstone block gets removed the piston retracts.
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That's a intentional thing dude. Please remove this bug report, they could really get it wrong and remove stuff from mincraft AMD it could hurt the game
This bug is called "quasi-connectivity" (you can read up how it came in existence, maybe the search term "Jeb Door" will help there), and it stuck around since then.
For apparently many beginners and even for some advanced Redstoners it does not make any sense or is an annoyance for them, however, this is MC-108, and currently it does not look as if this bug would get fixed. Some people who use this bug would - to put it politely - give Mojang a hard time, if they would remove QC.
There is a little hope that, one day, the Redstone system will get an overhaul, and where there would hypothetically be also QCless options, so people like you who find this behaviour illogical can build their contraptions the way they think makes the most sense, without QC getting in the way.
I'd suggest to watch slicedlime's snapshot videos, as he would inform of any changes. If you got Twitter, following Java MC Devs would also be a good idea, especially Java Tech Devs.