According to Avianca's document checker, a US citizen visiting Nicaragua for a brief visit for purposes of tourism must fill out the Solicitud de Ingreso y Egreso form in advance of travel. However, Timatic lists no such requirement, while the US State Department splits the difference, saying that non-tourist visitors are recommended (but apparently not required?) to fill out the form.
Which of these sources are right? What do I do if Avianca insists I submit the form but the Nicaraguan govenrment does not care?
I am aware of the separate requirement to have US$10 in cash to pay for a tourist card upon arrival; this question is only about any actions I might need to take before boarding a plane.