In the garage in Apeldoorn the mechanic measures your rear tyres: tread depth 2.0 mm in the main grooves, both the same size, no visible carcass — but one tyre has a clear bulge on the side. Is this tyre approved?
No — a bulge is its own independent failure ground, separate from tread, size and carcass
Yes — tread, size and carcass are fine, so the tyre is approved
Explanation
Wrong — trap: tread-is-enough (here: other-requirements-are-enough). Bulges are their own independent requirement (the law); even without carcass damage the tyre fails.