Misleading Congress by weasel words is also illegal, with or without a formal oath:
https://www.gpo.gov/fdsys/pkg/USCODE-2014-title18/pdf/USCODE-2014-title18-partI-chap47-sec1001.pdf
...whoever,in any matter within the jurisdiction of the executive, legislative, or judicial branch of the Government of the United States, knowingly and willfully —
(1) falsifies, conceals, or covers up by any trick, scheme, or device a material fact;
(2) makes any materially false, fictitious, or fraudulent statement or representation...
... imprisoned not more than 5 years...
Too bad we don’t have laws on that (smirk).