Why summarize m'nachos in musaf?

Question

In every musaf prayer service, we read an excerpt from Bamidbar delineating the musaf animal sacrifices of the day. While each day's passage in Bamidbar includes also a description of the flour and oil offerings brought along with the animals, we don't read that excerpt, instead summarizing it; we use the same (or almost the same) wording every musaf prayer.

• Why do we summarize instead of finishing up the quotation we've started?
• Are there any nuschaos (versions) that do (or did) include the entire quotation rather than a summary?

The one exception is the musaf of Shabas, whose passage in Bamidbar we quote entire and do not summarize.

• Does the reason I seek above for summarizing not apply to Shabas? If it does apply, why don't we summarize the passage of Shabas also?
• Are there any nuschaos (versions) that do (or did) summarize the passage of Shabas as other days'?

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On later reflection: The reason we don't summarize the musaf of Shabas (my third bulleted question) is presumably that it'd require quoting half a pasuk a verbatim. But a source for that would be nice; and, anyway, that doesn't answer my first two (and last) bulleted questions.

Answer 1

According to this article, in Eretz Yisrael in ancient times they did recite the entire section for each Yom Tov (including the verses describing the menachos and nesachim). But because it's difficult to remember them (particularly before siddurim began to be written), in Babylonia the ומנחתם ונסכיהם paragraph was created to regularize the description of that part of the korban (which in the Torah has various subtle variations from day to day).

[Other Geonim held (based on Rosh Hashanan 35a, see Rashi there ד"ה כיון and אין צריך) that even that's not necessary; the Sephardic nusach to this day follows suit, and omits the pesukim of the korbanos (and ומנחתם ונסכיהם) entirely. On the other hand, Rashi eventually accepted the position of R. Meir Shliach Tzibbur (the author of Akdamus) that they should be recited, and this became the Ashkenazic practice.]

As for Shabbos, Rashi writes that its pesukim were always recited in Ashkenazic communities even before R. Meir came along, "because they are constant and [therefore] familiar." So there was probably also less of a need to use ומנחתם ונסכיהם to replace any part of those two pesukim. (Also, anyway it would be factually incorrect - דובר שקרים - to use it in its standard form, since there is no שעיר לכפר on Shabbos.)