That’s simply not true. Congress has the power to organize the executive branch, not the president. Congress created the agencies and departments and they cannot be closed by the president.

Edit:

Constitutional explanation: https://www.law.cornell.edu/constitution-conan/article-2/sec...

report on Congress control of executive branch agencies https://crsreports.congress.gov/product/pdf/R/R45442/2#:~:te...