Introduction: Documented consent without demonstrable comprehension is medicolegally insufficient, yet comprehension-based informed consent (IC) failure in collectivistic surgical populations is largely unquantified. Methods: This re-analysis of a previously reported cross-sectional dataset assessed IC efficacy among 320 consecutive adults undergoing high-risk elective surgery (ASA physical status III–IV) at Private Hospital X, Palembang, Indonesia, in 2024, reported per STROBE. Six instruments standardised to 0–100 were administered, including the IC Comprehension Score (ICCS) and the five-domain composite IC Efficacy Score (ICE); adequacy was ICE ≥ 70. Exact intervals and permutation tests, effect sizes, areas under the receiver operating characteristic curve recovered from Mann–Whitney U statistics, E-values, fragility indices, standardisation and a partial-identification audit were added. Results: Only 19 of 320 patients (5.9%, 95% CI 3.6–9.1) achieved adequate IC efficacy, below both published comparators reporting an explicit adequacy proportion (exact binomial P < 0.001 versus 14.0% and versus 35.8%); standardisation to lower-education distributions reduced this to 2.74–3.79%, so 5.9% is an upper bound. Adequacy rose monotonically across educational strata from 0.0% to 13.3% (exact Cochran–Armitage z = 3.66, P = 0.0003; tertiary versus secondary education or below, odds ratio 8.27, 95% CI 2.36–29.00; E-value 14.29; fragility index 8). ICCS was the only independent predictor in an exploratory multivariable model with 2.71 events per variable (odds ratio 13.75 per SD, 95% CI 3.32–56.92), an association partly constitutive because comprehension is one ICE domain. Neither family influence nor collectivism predicted adequacy. Conclusion: Comprehension, not cultural collectivism, gates valid surgical consent.