In the Runas example that uses "boulder" make it clear that "boulder"

is a host name.

doc/sudoers.cat

@@ -529,8 +529,8 @@ SSUUDDOOEERRSS FFIILLEE FFOORRMMAATT
 
      dgb     boulder = (operator) /bin/ls, /bin/kill, /usr/bin/lprm
 
-     The user ddggbb may run _/_b_i_n_/_l_s, _/_b_i_n_/_k_i_l_l, and _/_u_s_r_/_b_i_n_/_l_p_r_m--but only as
-     ooppeerraattoorr.  E.g.,
+     The user ddggbb may run _/_b_i_n_/_l_s, _/_b_i_n_/_k_i_l_l, and _/_u_s_r_/_b_i_n_/_l_p_r_m on the host
+     boulder--but only as ooppeerraattoorr.  E.g.,
 
      $ sudo -u operator /bin/ls
 
@@ -2868,4 +2868,4 @@ DDIISSCCLLAAIIMMEERR
      file distributed with ssuuddoo or https://www.sudo.ws/license.html for
      complete details.
 
-Sudo 1.8.21                     August 1, 2017                     Sudo 1.8.21
+Sudo 1.8.21                     August 4, 2017                     Sudo 1.8.21

doc/sudoers.man.in

@@ -21,7 +21,7 @@
 .\" Agency (DARPA) and Air Force Research Laboratory, Air Force
 .\" Materiel Command, USAF, under agreement number F39502-99-1-0512.
 .\"
-.TH "SUDOERS" "5" "August 1, 2017" "Sudo @PACKAGE_VERSION@" "File Formats Manual"
+.TH "SUDOERS" "5" "August 4, 2017" "Sudo @PACKAGE_VERSION@" "File Formats Manual"
 .nh
 .if n .ad l
 .SH "NAME"
@@ -1107,7 +1107,9 @@ may run
 \fI/bin/ls\fR,
 \fI/bin/kill\fR,
 and
-\fI/usr/bin/lprm\fR\(embut
+\fI/usr/bin/lprm\fR
+on the host
+boulder\(embut
 only as
 \fBoperator\fR.
 E.g.,

doc/sudoers.mdoc.in

@@ -19,7 +19,7 @@
 .\" Agency (DARPA) and Air Force Research Laboratory, Air Force
 .\" Materiel Command, USAF, under agreement number F39502-99-1-0512.
 .\"
-.Dd August 1, 2017
+.Dd August 4, 2017
 .Dt SUDOERS @mansectform@
 .Os Sudo @PACKAGE_VERSION@
 .Sh NAME
@@ -1056,7 +1056,9 @@ may run
 .Pa /bin/ls ,
 .Pa /bin/kill ,
 and
-.Pa /usr/bin/lprm Ns \(em Ns but
+.Pa /usr/bin/lprm
+on the host
+.No boulder Ns \(em Ns but
 only as
 .Sy operator .
 E.g.,