Why can't HorizontalGauge be directly added to the control part of Manipulate[]?

Question

I try to use HorizontalGauge in Manipulate as follows:

    Manipulate[
 Graphics[Disk[]],
 HorizontalGauge[Dynamic[x], {0, 100}]
 ]

but it didn't work. If I wrap the gauge with Row[], then it works. Can anyone explain why it works like this?

    Manipulate[
 Graphics[Disk[]],
 Row@{HorizontalGauge[Dynamic[x], {0, 100}]}
 ]

Answer 1

In Manipulate >> Details and Options allowed forms of the second argument are listed:

So HorizontalGauge[Dynamic[x], {0,10}] (or, for that matter, Slider[Dynamic[x], {0, 10}] or Checkbox[Dynamic[z]] or InputField[Dynamic[w]] etc.) is not allowed in the second (or later) argument.

The highlighted row of the list is elaborated on as

So using Row @ {HorizontalGauge[...], Style @ HorizontalGauge[...], Text @ HorizontalGauge[...] etc. do work.