Agency: Unvouchered expenses 'income'

The REPUBLICAN & Herald notes that two lawmakers paid taxes on their "unvouchered expenses." But I thought UEs are not "income" so as not to be a direct violation of the Consitution's prohibition against raising a lawmakers' income in the same term in which they passed their own compensation increase?

Apparently Sen. Rhoades and Rep. Argall recognized the money for what it was/is: Income. While we applaud them for paying their taxes, isn't this an admission of guilt in violating the Constitution--which, by the way, is the only pledge/oath our lawmakers must make to uphold?

Kind of a tough choice, I'd say. Either they become tax evaders or admitted violators of their oath of office. Guess the latter doesn't have many punishments--other than the voters' verdict at the ballot box.