In the article you have the perfect answer:
"Trump was admitted when the lease was signed entitling him to whatever benefits current and future and the Feds to whatever payments current and future and other terms. Change the terms of the contract during the Trump Presidency and you have a case Councilor. Your example of the Senator admission is the type of change in terms that is not permitted. It is not applicable to the current scenario. Prior to the inauguration both Trump and GSA abide the contract terms and each receives the benefits due. After inauguration, provided Trump and GSA continue to abide by the contract terms, each receiving only what is due, how has Trump been unduely enriched and how has the Government been harmed? Where is the wrong requiring correction? Also no doubt there is a termination clause; what say it? Termination could enrich Trump at the expense of the Government and that would seem to harm the Government. On a side note, it seems unlikely a GSA clause in a civil contract would take precedence over the Presidential qualifications in the Constitution but maybe you can find an example. The extra-Constitution requirement for the President to divest property seems... unconstitutional but maybe you know of some legal example of extra-Constitution requirements found to be... Constitutional, please enlighten Councilor. The GSA clause may be unenforceable. "