For starters, Silver Sovereign is a 2-Star fish and generally considered the LEAST optimal way to get a Forager's Hat (and thus Mastercraft Demimateria). CRP has an option in the Forager's Rod but it needs 20 HQ Silver Sovereign which is completely unfeasible to deem it a reliable source (I got a Field3 from mine btw). There's a thread on this over in the Item&Synth section (or maybe it was the DoH?) with a far more indepth detailing on how unbalanced the gains for MDM is between the various classes.

As for people saying it's balanced by how say Field3 is easier to obtain for some (mainly LTW and WVR). In terms of cost the bridesmaid/bridesgroom are not very cost efficient for Field3 compared to what they sell for on market board. GSM also has really easy access to these in the glasses that can be made from very cheap and easily accessible materials (especially if you bother killing some imperials yourself for them). Fieldcraft and Mastercraft materias are NOT balanced at all among all the classes in availability or ease of gaining and people who say they are, are outright ignorant.