It's not terribly clear to me what your question really is, but there are various types of memory. What is suspected is that the Japanese tests in question are in fact a test of eidetic (aka photographic) memory, and not of working memory (WM), but this is based on "anecdotal evidence" that performance in those Japanese tests was not affected by attentional interference like most WM tests are (e.g. having to recall which physical boxes in a set have been searched for food).

Previous studies focusing on WM performance in chimpanzees used serial learning paradigms in which participants learn to touch an array of stimuli in order (e.g. Arabic numerals) through extensive, step-wise training. Following this training, the array was masked once the subjects touched the first numeral in the sequence [38,39]. One juvenile chimpanzee mastered this masking condition with nine numerals on the screen. When chimpanzees were exposed to the stimuli for a predefined time interval before each trial (210–650 ms) [39], the shortest exposure time of 210 ms did not impair the performance of the best-performing juvenile (with five numerals on the screen). The authors suggested that apes' performance in this study might be based on an eidetic memory strategy [40], the ability to recall an image after only a brief moment of exposure. Similarly, Carruthers [6] argued that chimpanzees performance in this case might reflect a form of sensory short-term memory. Important task demands that distinguish short-term memory tasks from WM tasks, such as resistance to attentional interference (induced, for example, by a secondary task) or the continuous updating of memory contents, were not part of the research design. However, anecdotal evidence suggested that chimpanzees’ performance in this task was not susceptible to attentional interference [38,39].

It's not terribly clear to me what your question really is, but there are various types of memory. What is suspected is that the Japanese tests in question are in fact a test of eidetic (aka photographic) memory, and not of working memory (WM), but this is based on "anecdotal evidence" that performance in those Japanese tests was not affected by attentional interference like most WM tests are (e.g. having to recall which physical boxes in a set have been searched for food).

Previous studies focusing on WM performance in chimpanzees used serial learning paradigms in which participants learn to touch an array of stimuli in order (e.g. Arabic numerals) through extensive, step-wise training. Following this training, the array was masked once the subjects touched the first numeral in the sequence [38,39]. One juvenile chimpanzee mastered this masking condition with nine numerals on the screen. When chimpanzees were exposed to the stimuli for a predefined time interval before each trial (210–650 ms) [39], the shortest exposure time of 210 ms did not impair the performance of the best-performing juvenile (with five numerals on the screen). The authors suggested that apes' performance in this study might be based on an eidetic memory strategy [40], the ability to recall an image after only a brief moment of exposure. Similarly, Carruthers [6] argued that chimpanzees performance in this case might reflect a form of sensory short-term memory. Important task demands that distinguish short-term memory tasks from WM tasks, such as resistance to attentional interference (induced, for example, by a secondary task) or the continuous updating of memory contents, were not part of the research design. However, anecdotal evidence suggested that chimpanzees’ performance in this task was not susceptible to attentional interference [38,39].

Anyhow, in the food boxes search types of test, some chimpanzees exceed the (WM) ability of the average 7-year old human child. (Same source.) And since the latter kind of test doesn't use any screens...