Well, that's kind of expected. The most obvious solution to this is to forgo physical issues completely for the time being, but Jump is still so stuck on physical sales they're not actually willing to.
The problem isn't physical issues. That's just a matter of sending the completed issue off to the printer. All forgoing them would accomplish would be to enable Jump to move deadlines forward a few days, which would only help for one week before the new deadlines became the new normal. The real bottleneck is preparing the issue.
Here's a fun way to illustrate the issue.
In To Love-ru, Rito's father Saibai is a mangaka. He maintains a separate apartment as his studio with a bunch of drawing supplies and reference materials scattered about, and spends many hours a day working in a small space with his assistants all sitting right next to each other. I'm not sure if it ever comes up in the series, but presumably his editor either drops by the studio to discuss upcoming manuscripts, or Saibai goes to his editor's office at the publisher to discuss them. That's a good example of how mangaka had to work in the early 2000s.
In Yuragi-sou no Yuuna-san, Nonko, one of the tenants of the Yuragi Inn is a mangaka. Nonko does her job on a computer and drawing tablets in her room where she works. Her one assistant at the start of the series works remotely, and doesn't actually meet Nonko in person until the company Christmas party. Eventually Nonko gets another assistant who works in the same room due to their own preference. Nonko's editor takes a long train ride to meet with her, purely due to personal preference(and for an excuse to use the hot spring) as Nonko's manuscripts are submitted over the internet. That's a decent enough example of how mangaka can work in the late 2010s.
Mangaka who work like Saibai are the ones most affected by this. Their workflow involves a few to several people being in the same room together for hours and hours at a time. Likely using public transportation to get there. The necessary meetings with the editor require either editor or mangaka to go to the other, again probably using public transit. Taking measures against infection will royally fuck up their workflow. Fewer or no assistants, meaning fewer pages, lower quality art, or random breaks while they bring the chapter up to acceptable quality. Trying to set up videochat meetings with the editor instead of doing face to face meetings. Figuring out how to get the final manuscript sent electronically instead of it being personally delivered by the mangaka/an assistant or picked up by the editor. Not doing physical printings of the issue won't help them.
Mangaka who work like Nonko are the ones least affected by this. They just have their assistants work purely from home. They switch to always meeting their editor via videochat. Submitting the finished manuscript doesn't change for them. Physical prints of the issue are entirely irrelevant to their work as they don't need the help.
Now, this illustration leaves out the mangaka who are in between. Some do the drafting of a chapter with pen and paper, meet with their editor in person, then do the rest digitally. Others work all digitally, but meet with the editor in person, and aren't set up to have their assistants work remotely. Mangaka like this will have some disruption to their workflow, but won't be as bad off as the ones who were purely analog still. Again, forgoing physical printings doesn't help them.
The other undiscussed point is the editors. They meet to compile the issue. Skipping physical issues in favor of only doing digital issues won't help them, as they still need to meet and compile the issue. What would help them is working out how to meet via videoconferencing instead of in person to do the necessary work, but they're probably already figuring that out as part of this.
All in all suspending printed issues does nothing for them. What would help them is a switch to video conferencing and working remotely, and all of the mangaka going full digital. Which is not something that happens quickly and easily without issue if they weren't already set up for them. For the mangaka in particular, moving from analog to digital is a major transition with a significant learning curve that would slow them down or reduce the quality of their work while they made the switch. Thus we have the editorial department warning ahead of time that there may be problems in the near future.