Visalife

POE = Port of Entry as those arriving on an immigration visa such as a CR1 activate their Green Card upon entry in the US using that visa.  In your case your spouse must have entered the US on June 15th 2019 based on the date on the GC so I assume your spouse filed the N400 on or after March 17, 2022.  Stranger things have happened, but I doubt USCIS will be ready for an N400 interview in a month or two (you didn't give the date of the scheduled ROC interview).
 
Good Luck!

wow 
fast process to do from PD date of April 2019 to june 2019 green card

What would an attorney do differently than if we just presented with a copy of all relevant evidence? Interview is in a few days, is it really a risk to go without an attorney?

And to give you some more ammunition IF you get stuck in delays, please read a post made by VJ member @Libertate where detailed contact and info is given AIC ( American Immigration Council) is offering FREE legal rep for cases and class action lawsuit upcoming for the delays. Someone should definitely ask @Crazy Catto investigate directly w AIC and perhaps put a spotlight on who can get help. 
 
 

Thanks for the responses, this is probably what we'll do then, especially since we're not certain they are even planning a combo interview. Appreciate your help!

Excellent suggestion given the recent denial for” marital union “

That reference number will be useful in case you get denied based on a "no show".
 
Ideally, your online status will change when they schedule the interview and you'll receive your notice at home. 

Yes. 

The risk is to find out there was an interview and you failed to appear once you receive the denial. 

There's a risk of you not receiving the new interview notification.  Keep checking the case status online often and sign up for USPS informed delivery.
 
There's a recent post in the forum of a case being denied after rescheduling. They were able to reopen the case, but it was quite stressful for the couple.