In order to advertise a route it must be in your routing table. Not just contributing routes, but the actual aggregate route you want to advertise.
Both methods you note will work. If the aggregate is a valid OSPF route then your term of both protocol ospf and the route filter together will pull in the route for advertisement. (there are some minor syntax errors in your commands).
Also creating the static reject or discard route is a common method to get the route into the table for use as an advertisement. So that will work too.
Your other options are to create an aggregate route which will only be in the table when contributing routes are present and drop when they are not. Or a generated route which behaves the same way but can inherit the next hop from a contributing route instead of being reject or discard so it can forward traffic.