The issue was fixed as noted in the commits listed previously, just not exactly as you suggested. See lines 230-253 in tlsIO.c:

	if (ret <= 0) {
	    if (rc == SSL_ERROR_WANT_CONNECT || rc == SSL_ERROR_WANT_ACCEPT) {
		bioShouldRetry = 1;
	    } else if (rc == SSL_ERROR_WANT_READ) {
		bioShouldRetry = 1;
		statePtr->want |= TCL_READABLE;
	    } else if (rc == SSL_ERROR_WANT_WRITE) {
		bioShouldRetry = 1;
		statePtr->want |= TCL_WRITABLE;
	    }
	}

	if (bioShouldRetry) {
	    dprintf("The I/O did not complete -- but we should try it again");

	    if (statePtr->flags & TLS_TCL_ASYNC) {
		dprintf("Returning EAGAIN so that it can be retried later");
		*errorCodePtr = EAGAIN;
		return 0;
	    } else {
		dprintf("Doing so now");
		continue;
	    }
	}

-------------------

I just tested it with the below script on both Windows and Linux and it worked on both. See below:

-------------------

Script

package require Tcl
package require http
package require tls
::http::register https 443 ::tls::socket

set token [::http::geturl https://localhost:8143/info -timeout 3000]; # use port with no service listening here!
http::status $token


-------------------

OpenSUSE 16.0

Brian@Blizzard:~> /usr/bin/tclsh
% package require Tcl
8.6.17
% package require http
2.9.8
% package require tls
2.0
% ::http::register https 443 ::tls::socket
443 ::tls::socket
% set token [::http::geturl https://localhost:8143/info -timeout 3000]; # use port with no service listening here!
connect failed connection refused
% http::status $token
can't read "token": no such variable
% exit

Brian@Blizzard:~> /opt/tcl9/bin/tclsh9.0
% package require Tcl
9.0.3
% package require http
2.10.1
% package require tls
2.0
% ::http::register https 443 ::tls::socket
443 ::tls::socket {} 0 0
% set token [::http::geturl https://localhost:8143/info -timeout 3000]; # use port with no service listening here!
connect failed: connection refused
% http::status $token
can't read "token": no such variable
%

-------------------

Microsoft Windows [Version 6.1.7601]
Copyright (c) 2009 Microsoft Corporation.  All rights reserved.

C:\Users\Brian>c:\TCL\bin\tclsh
% package require Tcl
8.6.14
% package require http
2.9.8
% package require tls
2.0
% ::http::register https 443 ::tls::socket
443 ::tls::socket
% set token [::http::geturl https://localhost:8143/info -timeout 3000]; # use port with no service listening here!
connect failed connection refused
% http::status $token
can't read "token": no such variable
% exit

C:\Users\Brian>c:\TCL9\bin\tclsh
% package require Tcl
9.0.3
% package require http
2.10.1
% package require tls
2.0
% ::http::register https 443 ::tls::socket
443 ::tls::socket {} 0 0
% set token [::http::geturl https://localhost:8143/info -timeout 3000]; # use port with no service listening here!
connect failed: connection refused
% http::status $token
can't read "token": no such variable
%