Is uttering the Two Testimonies a precautionary measure, after some friends said that it is obligatory to interpret the attributes of Allah and that not believing so is disbelief (kufr), leading to apostasy from Islam or a defection that necessitates repentance?

What the questioner mentioned about uttering the two testimonies or not interpreting the attributes is not disbelief (kufr) or apostasy (riddah). The fear of disbelief is praiseworthy, but it must be placed in its proper context. Ruling that interpreting the attributes of Allah is obligatory is an error, and declaring someone who does not do so a disbeliever is extremism. The methodology of the Salaf is to affirm the attributes mentioned in the Qur’an and Sunnah and not to interpret them unless there is a strong evidence.