Claim 1 by the "Professor" of law (as reported by @NewsWireLK )
"President will have to report to courts and will not be able to efficiently serve the public"
This is FALSE the President does NOT report to Court. The cases are instituted against the AG who represents Pres. (1) https://twitter.com/NewsWireLK/status/1303651324664246272

Claim 2: "The President was made to appear before various commissions and courts prior to his election. If he is to appear before such courts and commissions after being elected as the President, he will not have sufficient time to implement pledges made". This is also FALSE (2)

As the Constitution stands today. The ONLY proceedings in which the President's action can be challenged are before the Supreme Court in a Fundamental Rights application. The President isn't required to be there in person. S/he is represented by the AG. (3)

Even under the proposed 20A the acts of the President in his capacity of a Minister can be challenged in Court. The amount of effort the President will have to give personally for this process is the same as he has to do today. So the "Professor's" argument makes no sense. (4)