Doesn’t matter if you don’t fancy drilling all those corners, you HAVE to, it’s the right procedure these days. Use a 10-12mm core bit, M14 thread for your angle grinder, it’ll blast a hole through in moments. Drill as close to the intersection of the corner as you can, this way it will help prevent the tension within the tile continuing in a straight line, an arc prevents that, hence drilling the corner.
It used to be an issue exclusively for larger formats, not so much the case these days.
That notwithstanding, your tiles could be just tensioned, full stop!
Then you’re not going to achieve L cuts, the lot will have to be exchanged for a new batch.
No matter what you try, even waterjet cutting won’t work if they’re that bad.
At some point, and if your experienced enough, you’ve gotta say, hang on, it’s not me it’s the tiles.
Drill a couple first and try that, see what happens.
You can also drill them, and cut 10mm in to the tile at the edge then stop and cut from the core hole outward toward the edge.
And if it still happens, last thing is to core a sizeable hole, 40-50mm and seewhat happens then.
Sometimes, it just can’t be done if they’re tensioned too much.
Only experience can tell you at which point to say “enough is enough”
Badly tensioned tiles normally present themselves by having a darker biscuit than normal, flatter backs and can be heavier than a non tensioned one.
Also when it splits, if one side of the split springs up and away as it happens, it’s another tell tale sign. Basically, the two bits won’t fit perfectly together again, it’ll be raised somewhere along the split.