Student or Learner
1. Rumors say that ...
2. Rumor has it that ...
Are these two interchangeable?
Vibe - Google ブックス
Rumors say that Fat Joe plans to disband the Terror Squad to free his own star power of dead weight. But standout Remy should still see her solo release. ...
Frommer's Las Vegas 2005 - Google ブックス
Rumor has it that the company that bought the other hotels from the family who still owns the El Cortez has an option on it as well, and that all of them ...
"Rumour has it that X..." is the ordinary idiom; it implies a cautious attitude towards the rumour, on the part of the speaker.
"Rumours say that X..." is much less common, and perhaps not quite as natural for most speakers; it does not tell you anything about the attitude of the speaker towards the rumour.
Not a professional ESL teacher.