I don't think the rules summary covering mortars is correct. They only fire like artillery (except target hex only) if using the indirect spotting rules. If using the direct fire method, they fire like any other unit but have an underlined firepower and can't target hard targets (no AP firepower). Page 6, Mortars.
The way it currently reads is that they use the artillery fire procedure all the time.
Per the rules, mortars can target hard targets as seen in their "ability to bombard soft as well as hard targets" (see the first sentence on mortars in section 6.1, page 11). Their ability to affect hard targets was a bit too good, which led Mark Walker to agree on ConsimWorld to add the rule that the best a mortar can do to a hard target is disrupt it.
On page 4 of the rules summary, in the Ranged Combat section, I covered direct fire under "Mortars" while covering their use of the artillery fire procedure under "Mortar Spotted Fire".
I think the rules summary is clear, but I'm open to suggestions on wording and corrections. I'm finding the summary to be quite helpful in my Vassal pbem play.
Don't have my NaW rules handy, but if that is the case, it's a major change from the WaW series. I just checked in the Blood and Bridges rules and they have no such provision for mortars.
FWIW the online rules don't mention mortars in 6.1 either except for listing them as soft targets. The online rules for 6.1 Ranged Combat are almost verbatim from the WaW series rules.
In WaW they can either fire directly but only at soft/soft-skinned targets (which went away in NaW) or they could fire indirectly but required a spotter and couldn't use opportunity fire. In the indirect case they followed the rules for artillery fire and could affect hard targets though with disruption only after some discussion about it.
I went and checked my WSR rules and your summary is correct. My apologies for creating the chaff. It is a fundamental change in the final ruleset for the series as a whole. It actually makes WW2 mortars more powerful than present day versions, odd to say the least.
I need to re-read the WSR rules more carefully before my next game, I skimmed them when I got my copy and incorrectly assumed that they made few changes to the WaW system.