The definition of uniform normality given is not a property of the underlying topology of your uniform space, but the definition of uniform normality is a property of the underlying proximity on your uniform space. Furthermore, the definition of uniform normality is correct since the uniformly normal spaces are precisely the uniform spaces where Tychonoff's theorem holds for uniformly continuous functions.
The reader is referred primarily to [2] for more information on proximity spaces. One should consult [1] for more basic information on proximity spaces.
If $(X,\mathcal{U})$ is a uniform space, then $(X,\mathcal{U})$ becomes a proximity space where $R\delta S$ if and only if $D[R]\cap D[S]\neq\emptyset$ for each $D\in\mathcal{U}$. Said differently, $R\overline{\delta}S$ if and only if $D[R]\cap D[S]=\emptyset$ for some $D\in\mathcal{U}$. The definition of $\preceq$ is the same as defined before. In particular, $R\preceq S$ if and only if $D[R]\subseteq S$.
$\textbf{Proposition}$ Let $(X,\mathcal{U})$ be a uniform space. Then the following are equivalent.
$(X,\mathcal{U})$ is uniformly normal (as defined in the question)
Whenever $C$ is a closed set, $U$ is an open set and $C\subseteq U$, then $C\preceq U$.
If $C_{1},C_{2}$ are two disjoint closed sets, then $C_{1}\overline{\delta}C_{2}$.
$R\overline{\delta}S$ if and only if $\overline{R}\cap\overline{S}=\emptyset$.
$R\preceq S$ if and only if $\overline{R}\preceq S^{\circ}$.
Furthermore, if $(X,\mathcal{U})$ satisfies any of the above conditions, then $X$ is normal as a topological space.
Recall that any compact space has a unique uniformity and a unique proximity. Therefore when talking about uniformities and proximities on compact spaces, there is no need to mention the uniformity on proximity in question. The following proposition can be found in [2][Cor. 12.12].
$\textbf{Proposition}$ If $(X,\mathcal{U})$ is a uniform space and $C$ is a compact Hausdorff space, then a function $f:(X,\mathcal{U})\rightarrow C$ is a proximity map if and only if it is uniformly continuous.
Using the above characterization of the bounded real-valued uniformly continuous functions, we obtain a few more characterizations of uniform normality by replacing "uniformly continuous" by proximity map.
$\textbf{Proposition}$ Let $(X,\mathcal{U})$ be a uniform space. Then the following are equivalent.
$(X,\mathcal{U})$ is uniformly normal.
If $C_{1},C_{2}\subseteq X$ are disjoint closed sets, then there is a uniformly continuous map $f:X\rightarrow[0,1]$ with $f|_{C_{1}}=0$ and $f|_{C_{2}}=1$.
$X$ is normal and every uniformly continuous map $f:X\rightarrow[0,1]$ is continuous.
$X$ is normal, and for every compact Hausdorff space $C$, every uniformly continuous map $f:X\rightarrow C$ is continuous.
Willard, Stephen. General Topology. Reading, MA: Addison-Wesley Pub., 1970.
Naimpally, S. A., and B. D. Warrack. Proximity Spaces. Cambridge Eng.: University, 1970.