Dynamic mangle change-mss rules for l2tp client

Hello everyone.

I’ve created l2tp client with change-tcp-mss=yes option in profile.
But the only one dynamic mangle mss rule is created automatically - only for in-interface:

/ip firewall mangle print dynamic 
Flags: X - disabled, I - invalid, D - dynamic 
 0  D chain=forward action=change-mss new-mss=1420 passthrough=yes tcp-flags=syn 
      protocol=tcp in-interface=all-ppp tcp-mss=1421-65535 log=no log-prefix=""

Why the second analog rule is not created automatically for the out-interface?

Now I have to create that second rule manually to surf sites witout errors.