I always thought that it does matter. For example, a relationship between doctors and appointments, with 50 elements in doctors and 500'000 elements in appointments, meant to "find" today's appointments, can be formulated as

DocID = docID

gDate = AppointmentDate

or as

gDate = AppointmentDate

DocID = DocID

In the first case, evaluating the first condition restricts results to 10'000, the second one should apply on this and deliver.

In the second case, evaluating the first condition restricts the results to 1'000, then comes the second one which has less work to do because the data it has to work on is 10 times less.

If the order does not matter, the discussion ends.

If it does matter, the discussion continues, because I have a relationship that fires a 5-second search on browsing from record to record.

if FMP uses SQL under the hood and you look at the SQL order of operations for tsql (as a model) one might conclude that order of the lines in the relationship graph and the equality operators do not have any significant impact..

if it does not use SQL under the hood then all bets are off.

Operator Precedence (Transact-SQL) | Microsoft Docs