According to Shintaido instructor Giovanni Rossi, our general natural tendency is to inhale when we extend our arms upward or outward and to exhale when we bring our arms downward or closer to ourselves. For example, observe your natural tendency to inhale when reaching up for something on a high shelf.
In contrast, when practicing Tenshingoso, in conjunction with vocalizing, we exhale while our hands and arms are extending upward or outward. So because of the vocalizing, Tenshingoso is certainly a form of breath control or a breathing technique (even if the method of breathing is never explicitly mentioned).
In other words, we can consider any way of breathing which is different from what we tend to do without any special training or practice as "breath control" or a breathing technique. This raises the question of whether Tenshingoso can be considered a type of qigong (氣功, sometimes also transliterated ch'i kung). Qi (Japanese ki) can be translated as "life force energy," while gong means "skill acquired through training". Generally, qigong is a Chinese discipline associated with both martial arts and health exercise that encompasses a broad range of methods for working with the life force.
I can say from experience that Chinese recognize some Shintaido techniques as qigong. During a trip to China in 1987, Michael Thompson and I visited the Beidaihe Qigong Rehabilitation Hospital of Hebei Province (Hebeisheng Beidaihe Qigong Liaoyang Yuan, 河北省北戴河气功疗养院). In spite of not having a letter of introduction (de rigueur in China), we were graciously received and the director met with us and gave us a quite enthusiastic and detailed explanation of qigong and its medical applications. Unfortunately a lot of it was beyond my linguistic capabilities, but one main point stuck clearly in my mind:
True qigong consists of the harmonious integration and disciplined training of three elements: