Sometimes I do still get requests with their useragents, but generally from implausible IPs (residential IPs, or "Google-Extended" from an AWS range, or same IP claiming to be multiple different bots, ...) - never from the bots' actual published IP addresses (which I did see before adding robots.txt) - which makes me believe it's some third party either intentionally trolling or using the larger players as cover for their own bots.