I can guess that Seared stone is a tile entity (probably for the smeltery) but it doesn't really do anything.

If you know it's a TileEntity, why do you even open this issue for 1.12?
To make you feel a bit more comfortable, we are working on Tiles for 1.14
I am not sure it is. That is just a guess.
Ok, we'll verify that then. If it isn't then there's something wrong
I am not sure it is. That is just a guess.
A quick test would be try to use a piston on it.
Or just press f3 haha
I always forget that's a thing
I am not sure what to look at in F3 debug screen, but a piston does move it.
I am not sure what to look at in F3 debug screen, but a piston does move it.
Almost forgot this: do you have Quark/Redstone++ installed and enabled (on by default) movable tile entities?
Quark supports movable tile entities by default, but some packs disable it because it causes crash on a lot of mods like RFTools.
Screenshot f3 mode whilst looking at the block :)
Quark is in the pack

Why are we doing all this again?
Just do some quick lookup on Github and I found this: https://github.com/SlimeKnights/TinkersConstruct/blob/1.12/src/main/java/slimeknights/tconstruct/smeltery/block/BlockEnumSmeltery.java#L41-L45
Basically all seared components are tile entities. Including all variants of seared stone.
That would of course have been too easy... Because why would we do something that makes sense/is easy?
Well, I'm sorry then but it's invalid on intention.
Most helpful comment
Why are we doing all this again?
Just do some quick lookup on Github and I found this: https://github.com/SlimeKnights/TinkersConstruct/blob/1.12/src/main/java/slimeknights/tconstruct/smeltery/block/BlockEnumSmeltery.java#L41-L45
Basically all seared components are tile entities. Including all variants of seared stone.