read-only intent with SQL Server availability group

When attempting to connect to SQL Server 2016 availability group listener,
I'm seeing a "Unexpected EOF from the server" error if read-only intent is
specified (this can be done via the freetds.conf file, for example). This
is using the latest dev1.00.308 code and an availability group with a
single secondary replica.

The failure seems to come from the listener closing the connection after
sending an ENVCHANGE routing message (type 20) message to the client. See
https://msdn.microsoft.com/en-us/library/dd303449.aspx

From my reading of the TDS protocol specification, it seems as though a TDS
7.1 client and later should handle the ENVCHANGE routing message and
reconnect to the host specified in the routing message when the read-only
intent flag is set.

Isn't the whole point of the read-only intent flag so that clients can be
routed to read-only replicas when possible? Note that FreeTDS does connect
successfully to the secondary (read-only) replica, and writes to it fail as
one would expect.