No, attributing a statement to three scholars only does not constitute consensus (ijmā', Arabic: إجماع), or any level of consensus for that matter. However, one has to read the full text of the fatwas to understand their content and context.
The first fatwa in Majmū' al-Fatāwa 26/195 (Arabic only) attributes the words to Imam Ibn al-Munādi. Referring to the fatwa by Ibn al-Munādi, one finds he prefaced his fatwa with "there is no known disagreement among the scholars" (Arabic: لا خلاف بين العلماء) to provide his definition of ijmā'. You may have noticed that almost always this is how scholars word their fatwas to refer to ijmā', which is defined as no disagreement among accredited scholars ('ālim mu'tabar, Arabic: عالم معتبر) for lack of a better term in English.
The second fatwa in Majmū' al-Fatāwa 7/586, likewise, quoted Ibn al-Munādi (same exact reference as in the first one). It then adds that the same ijmā' is agreed upon by Ibn Hazm and Ibn al-Jawzi. Again, you will find that Ibn Hazm's fatwa starts with "No Muslim imam that deserves to be called imam based on knowledge, may Allah be pleased with them, denies the sphericity of the Earth" (Arabic: أن أحداً من أئمة المسلمين المستحقين لاسم الإمامة بالعلم رضي الله عنهم لم ينكروا تكوير الأرض) as per the Islam Q&A article you quoted. This is Ibn Hazm's definition of ijmā'.
So, in conclusion:
- The fatwas do not attribute ijmā' based on the opinion of the three scholars; rather, it attributes to these scholars that they declared there was ijmā' to either the affirmation that the skies and Earth are spherical (Ibn al-Munādi), or to the lack of rejection of their sphericity (Ibn Hazm).
- Ijmā' was defined as "no known disagreement among scholars" rather than the layman understanding of "all scholars agree" by these scholars in their fatwas.
The first fatwa also quoted Imam Ibn Hanbal. On another note, he was quoted saying "whoever claims consensus is a liar" (see Tuhfat al-Mas'ūl 2/220), which led some laymen to think that he rejected ijmā', which is not the case as explained on the same page right after the quote.