I've noticed that couple of my aikido "sensei" (or "instructors") say" there's no 'combat
' in aikido."
That sounds like euphemism, clinging or being "attached" to a word, just semantics.
Aikido is martial: the physics of aikido studies violence for protection, self-defense, & combat, and even "fighting" for the purpose of saving life, reduce suffering, & restore or promote peace. Granted the main stream aikidoka mindset eschews competition, sports, and prize fighting. Nevertheless, for yudansha aikidoka, open-minded unpredictable "sparring" or kumite might add joyful practice that may enhance confidence, if you don't mind having to heal from inevitable and unintended training injuries from time to time.
Full disclosure: I am an aikido neophyte.
I understand that in order to acquire the waza skill, we, mudansha, must train slowly and carefully, with cooperation, at the kihon level, to first hone the basics. But eventually, when forced to, will want to move at the appropriate speed of "combat," physically "harmonizing" with resistance? So then, isn't an aikido form of "jissen or jiju kumite" be useful for advanced aikido students??