Just to complicate matters,
I used to have my lathe bolted to the floor, but have now removed the bolts.
I noticed that between summer and winter, there was a definite twisting effect that was produced by the bolting down. Since the bolts were removed a few years ago, the bed hasn't moved, and is is checked fairly frequently, and it doesn't go walkabouts.
You can buy anti vibration pads that the machinery sits on, these do stop walkabout if the machine has a tendency to go that way. But they are usually fairly expensive, and are rated by the weight of the machine.
Also, if you are bolting down, you should have levelling screws next to the bolt down holes. The lathe is levelled first, then bolted down, then the level rechecked and adjusted as necessary. If there is a lot of unevenness on the floor you are liable to put a permanent twist in the bed if you are not careful, especially on an all cast one like yours. The ones on cabinet stands are not prone to this as the stand usually flexes a little. Then you shim under the lathe to stand mountings to get to level. That is how mine is done.
Hope it hasn't confused you any more than necessary.
John