I guess that I'll have to wait until the next time that updates are available to see if App Store is behaving. I updated to iTunes 12.3.5 via App Store and App Store was behaving normally, except that it did not list updates installed in the last 30 days.
Jon
macOS 11.7.10, iMac Retina 5K 27-inch, late 2014, 3.5 GHz Intel Core i5, 1 TB fusion drive, 16 GB RAM, Epson SureColor P600, Photoshop CC, Lightroom CC, MS Office 365
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