The bearings are also relatively short. Even if they are free of backlash it would be e.g. easy to flex the Z-axis forward and backward.
Even more critical is the axis moving the base plate: it will tilt forward and backward easily unless it is supported by something else.
If the bearings aren't free of play its gets worse: you wouldn't even need force to flex the machine considerably. So besides a larger diameter using 4 instead of 2 bearings per axis (so that there are always 2 bearings on one shaft with some distance between them) would also be reasonable.
However - if you just like to mill some soft wood with small diameter tools it should be OK to have some fun with it - but use at least 4 bearings for the base plate - its just $5 more.
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