Hello. I have a rule: By my understanding it should work like this:
When there is traffic to address 192.168.120.250 on port 80 add src-address to address list named test2.
Is my reasoning wrong? Currently it always adds src-address to this address list even when there is absolutely no traffic to 192.168.120.250.

Yes.
Traffic to address 192.168.120.250 on port 80 from src-address-list=test add src-address to address list named test2.

That's what I want to achieve but it is not working.

what version ?
use bridge?

Use Torch in the relevant interface and check that there is really no such traffic.

RouterOS 5.26 but I also checked with 6.7(on another MT)
WAN is PPPoE client on ether1. On this MT there are PPPoE Server and MetaROUTER with web server. 192.168.120.250 is an address of MetaROUTER.
PPPoE Server is running on BRIDGE which consists of wlan1 and vif1.
I used torch on pppoe interface of the client and there was no traffic to 120.250.

Edit:
I checked with torch on pppoe interface of MetaRouter and here there is traffic from that ip. In torch for client pppoe it shows as an address for the destination because of dst-nat. Is there a way to limit this rule just for webpages?