Missing documentation regarding standard HyperShift behaviour. Node pool taint updates do NOT trigger a rolling replacement of nodes. Node taints, as well as labels, are applied only to new nodes. Existing nodes keep their original configuration. 
This is the observed behaviour, but can't be verified through current upstream documentation. 
This behavior is confirmed to be expected in:
https://redhat-external.slack.com/archives/C01C8502FMM/p1773161996368249

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ARO HCP Documentation uses ambiguous and misleading description:
To set a taint, specify a key, value, and effect. Available effects include the following:

NoSchedule PreferNoSchedule NoExecute
 
For example:
 
taints: [
  {
    key: 'key1'
    value: 'value1'
    effect: 'NoSchedule'
  }
]
 
This list overwrites any modifications made to node taints on an ongoing basis.