Hostile mobs (including creepers) are spawning in sufficiently lit areas inside player made houses caves in survival mode since Minecraft 1.16.0. for Windows 10. It is not due poor lighting because problem didn't happen in version 1.14.60 and earlier (the same map, the same interiors, sthe ame lighting provided enough light to not spawn mobs in these areas in Minecraft 1.14.60 (and ealier) for Windows 10).