These internal pull-ups (on all of those pins where they are) probably are reasonably weak (I'm guessing >50kohm).
So that implies that they work perfectly fine if pins are non-critical and left dangling *without* copper attached.
However, the CHIP_EN and nRESET pins are both critical, and usually have some copper attached due to you wanting to control them from the outside. The copper attached to the pins is subject to RF-spike-reception, and thus is able to pull that pin down momentarily despite the weak pull-up present.
So I'd recommend not relying on the internal pull-up for critical pins like CHIP_EN and nRESET. Other pins could be relied upon, if they have no copper attached only.
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