Many thanks for this detailed comparison of nut-cracking tools of captive chimps with Olduvai tools. Some possibly relevant thoughts.
All great apes at least occasionally make and use tools. Griphopithecus and many other early hominoids had thick molar enamel. The combination of stone tools use and thick enamel suggest at least some degree of durophagy. Around the time when hominoids crossed the Tethys, thick-enameled hominoids (griphopithecus?) are found in coastal sediments south (Saudi Ape "Heliopithecus" ad-Dabtiyah) as well as north of the Tethys (Slovakia "Austriacopithecus" Dev�nska Nov� Ves), they seem to have dwelt in coastal forests, where durophagy might have been not only for opening nuts (e.g. coconuts) but also for shell- & crayfish (e.g. capuchins have thick enamel & use stones or shell to open mangrove oysters). All this suggests Miocene great hominoids might have followed the Tethys coastal forests, where their diet included hard-shelled foods. Australopiths (still?) had thick cheekteeth enamel. Comparative data (esp. Alan Shabel) on australopiths show dento-gnathic convergences with durophagous carnivores (some dextrous mongoose and otters e.g. Aonyx). Statistically, australopithecines can't have been human ancestors or relatives to the exclusion of Pan and Gorilla: in that case, virtually all hundreds of hominid fossils had been close relatives of one extant species (H.sapiens), whereas the other 4 or 5 extant species (bonobo, common chimps, eastern and western gorilla) had had virtually no fossils. This is extremely unlikely, e.g. Asian great apes (Pongo) do have several fossil relatives (Siva-, Lufeng-, Khorat-, Gigantopithecus). In fact, all so-called "human" features in australopiths (e.g. thick enamel as in many Miocene hominoids, very small canines as in e.g. "Ramapithecus", low ilia as in monkeys, vertical lumbar spine as in gibbons, humanlike feet as in chimp fetuses) are not human-derived as often assumed, but are primitive-hominid, and lost in Pan and Gorilla ancestors. Probably the African apes had more vertical ancestors, not for running on 2 legs as often assumed anthropocentrically, but more likely for wading bipedally and climbing vertically in the branches in the wetlands where their fossils lay (google: aquarboreal). If many Mio-Pliocene hominoids (incl.australopiths) were swamp, flooded or mangrove forest dwellers (google: bonobo wading) this could help explain in australopiths the remarkable combination of curved manual phalanges, more humanlike flat feet (as in prenatal chimps) and "bipedality".
In conclusion, it's no surprise that many hominid tools had resemblances to chimp tools: many hominid fossil and archeological remains might have been closer to Pan or Gorilla than to us.