Why won't Windows 7 connect via L2TP/IPSec to pfsense?

Question

Windows

There is pfsense 2.4.5, acts as an L2TP/IPsec VPN server, located behind NAT.
On Windows, the built-in VPN client is used. Windows clients are behind NAT.
Clients on Win10 (1909) connect to the server via L2TP / IPsec, exchange keys via IKE, and then all traffic goes via ESP (as it should be).
Clients on Win7 do not even try to establish an IPSec connection and, when connected to the VPN server, they immediately start exchanging via L2TP (I found this out by allowing pure L2TP
connections on the VPN server). If L2TP without IPSec is disabled, then Win7 won't connect with error 809 (Supposedly, the VPN server is unavailable).

The VPN client settings on Win10 and Win7 are identical.

Registry key "AssumeUDPEncapsulationContextOnSendRule" set to "2"