That's remarkable. Where did you see that? Was it in Evan Thomas' "Ike's Bluff"
I'm fairly sure that it was either 'Summons of the Trumpet', one of the first post-war military histories or I think the title was 'an Illustrated history of the Vietnam War'. Both of these came out came out fairly early after the fall of Saigon. Summons of the Trumpet was said to be the first military history of the American involvement, as opposed to getting sidetracked into comtemporery politics and arguments about Lyndon Johnson's domestic program re; 'The Great Society' being undermined by the war etc. Or using bits of information to support the Authors take on the 'are the North Vietnamese really nationalists or really communists' and 'are the VC really independent of North Vietnamese control' controversies.
Yes it was a while ago when I read it, but the piece of information is, as you point out remarkable. The small numbers of US advisors present and low financial commitment can be checked elsewhere. That Eisenhower era photo's of the ARVN show them with WWII surplus half-tracks, rifles, etc while Kennedy era ones show M-113 APC's and the first introduction of the M-16 rifle show a difference in willingness to spend money. Statistics of Advisor numbers are also readily available, the jump in numbers getting people calling it 'The Quicksand War'.
But that Eisenhower deliberately kept his support down to one that he could walk away from with minimum risk to personnel is important. It could be removed without most of the ARVN troops in the jungle even noticing, most advisors were in bases and office buildings away from the fight. It makes the use of the term 'Eisenhower began America's commitment to Vietnam' look very dubious. JFK's much larger advisor force was very visible to the average South Vietnamese soldier, they were a secondary officer corps and pulling them out would be a clear sign the US had given up.