In the example you describe, the Community Taxon would be Asian Lady Beetle before B’s ID
So if B thought its not Seven-spotted but maybe Asian, he should not disagree with the Community Taxon.
But if B were to add an ID of Insects, the disagreement choices would be in regards to Asian Lady Beetle (not Seven-spotted Lady Beetle). In this example, neither would immediately impact the Community Taxon, but a ‘branch disagreement’ would add some additional disagreements to taxa like ‘Lady Beetles Family’ and ‘Seven spotted Lady Beetles’
while a ‘leading disagreement’ would not
so B would ‘branch disagree’ if they though the observation couldn’t be identified finer than Class Insects and would ‘leading disagree’ if they thought it was not Asian Lady Beetle but could be some other insect