Changing from True to False is tempting, but as Spamikonne says: it all depend on the internal structure of the code.
The risk is that a "False" condition can return a NULL (it means: nothing, not even "empty", simply not existing) value in a parameter if the programmer has not used a real boolean logic (True / False), the value "true" can be actually a string/variable value expected further in the code, not a boolean value. And the value False can be ignored as not part of an internal boolean condition.
A NULL value can then be associated to a parameter if the False condition is not understood/processed, and it can trigger an unhandled error in the code, at worst crashing the game, at best skipping a part of routine...
But it is also true (boolean...) that perhaps there is 90% of chance that it will work, and False may generate a correct value understood by the rest of the code.
Try, and if there is something abnormal happening, like the AI being much much smarter, there is definitely something wrong !!!!
If you look at the xml file you'll see in the table definitions at the top that "false" is the default value for the "ResearchAgreementTradingAllowed" column. Either deleting the line in the Philosophy entry or changing its value to "false" will accomplish the same thing and carries none of the risk you suggest. All the xml files are used for in this game is to load values into database tables. This is explained in the modding guide.
If doing this before a new game doesn't disable research agreements it may be a caching issue.
