"When Jesus, as He hung upon the cross, cried out, “ It is finished ,” the rocks rent, the earth shook, and some of the graves were opened. When He arose a victor over death and the grave, while the earth was reeling and the glory of heaven shone around the sacred spot, many of the righteous dead, obedient to His call, came forth as witnesses that He had risen. Those favored, risen saints came forth glorified. They were chosen and holy ones of every age, from creation down even to the days of Christ. Thus while the Jewish leaders were seeking to conceal the fact of Christ's resurrection, God chose to bring up a company from their graves to testify that Jesus had risen, and to declare His glory. EW 184.1"
"And the graves were opened; and many bodies of the saints which slept arose,"
The EGW passage directly references and expands upon the event described in Matthew 27:52, making it a clear explicit allusion.
"Those risen ones differed in stature and form, some being more noble in appearance than others. I was informed that the inhabitants of earth had been degenerating, losing their strength and comeliness. Satan has the power of disease and death, and with every age the effects of the curse have been more visible, and the power of Satan more plainly seen. Those who lived in the days of Noah and Abraham resembled the angels in form, comeliness, and strength. But every succeeding generation have been growing weaker and more subject to disease, and their life has been of shorter duration. Satan has been learning how to annoy and enfeeble the race. EW 184.2"
"There were giants in the earth in those days; and also after that, when the sons of God came in unto the daughters of men, and they bare children to them, the same became mighty men which were of old, men of renown."
Both passages discuss the stature and strength of people in the early days of earth's history. EGW connects this to degeneration and Satan's influence, while Genesis speaks of giants. There's a clear thematic overlap.
"they declared, “We be risen with Him.” They bore testimony that it was by His mighty power that they had been called forth from their graves. Notwithstanding the lying reports circulated, the resurrection of Christ could not be concealed by Satan, his angels, or the chief priests; for this holy company, brought forth from their graves, spread the wonderful, joyful news; also Jesus showed Himself to His sorrowing, heartbroken disciples, dispelling their fears and causing them joy and gladness. EW 184.3"
"But now is Christ risen from the dead, and become the firstfruits of them that slept."
Both passages deal with the resurrection of Christ and its implications for believers. EGW describes the risen saints testifying to Christ's power, while 1 Corinthians 15:20 speaks of Christ as the 'firstfruits' of those who have died. The theme of resurrection and its impact is present in both.