Non-sequitur.
The fact of whether Estonia was fit for purpose was the JAIC's remit.
No, establishing the cause of the sinking was their remit.
Part of that involves the condition of the ship when it sailed and it's design, construction, operational history, record of maintenance, inspection and certification.
They cover this at length in Chapter 3.
Have you actually read the report?
All of Chapter 18 is concerned with compliance with collision bulkhead requirements
From section 18.3 The role of the administration
https://onse.fi/estonia/chapt18.html
The Finnish Maritime Administration was, according to a national decree, originally issued in 1920 (3.6.4),
exempted from carrying out a hull survey as part of the basis for issuing the passenger ship safety certificate, if a vessel had a valid class certificate. The Administration did not therefore survey the hull construction during the building of the ESTONIA.The Bureau Veritas regulations for the initial hull survey included compliance with all applicable requirements specified in the rules of the society and valid at the time. These rules did not include requirements for an upper extension of the collision bulkhead, and hence no reference to the position of such an extension.
According to the Finnish Administration, the problem concerning the deviation of the ramp location from the SOLAS requirement for an upper extension of the collision bulkhead was not known to its inspectors.Anyhow, according to the same information, the Administration would have accepted the deviation in line with previous practice, applied also by the Swedish Maritime Administration.
The Commission has noted that full responsibility for enforcing compliance with the Conventions nevertheless, according to SOLAS, remains with the Administration. The Commission has also noted that the unrestricted right of the Finnish Maritime Administration to rely on classification society hull surveys in this respect was withdrawn in the new decree on surveys of ships issued in 1983.
It seems obvious to the Commission that the interpretation of the SOLAS Convention's collision bulkhead regulations common at the time did not ensure satisfactory compliance with applicable rules and made it possible to design the ESTONIA in a way which may have contributed to her capsizal. The Commission finds it unacceptable that practice is developed that makes it possible to deviate from a Convention with no documentation or exemptions in the certificate.