I think the issue is whether an individual's rights under GDPR are being honoured or not. If the applied filter doesn't allow for relatively easy bypasses that

I think the issue is whether an individual's rights under GDPR are being honoured or not. If the applied filter doesn't allow for relatively easy bypasses that demonstrates that either the data wasn't sufficiently corrected or deleted, then I think that would work. However, if an organisation claims to have removed that PII, but subsequently can leak it, then the filter is simply a band-aid and the organisation isn't GDPR compliant. There's also a major problem with LLMs if the training data includes PII that the individual never gave consent for it to be used for that purpose.