The word "cheat" in relation to competitive sport does not just mean breaking rules. People can be considered to be cheating if they break norms or customs or if they do things that one side may consider cheating but another side may not e.g. diving in football to gain a penalty, pulling on people's shirts to stop them reaching the ball etc
Sure I accept that 'cheating' may go beyond the precision of the rules that govern the sport to cover broader culture and ethos, but I really don't see how this helps you.
So to start with your examples - actually diving and shirt pulling are against the laws of football and players are often penalised for those offences, including receiving a yellow card. So those examples aren't really supporting your argument.
But on the broader issue of culture and ethos well it is the governing bodies of the sports themselves, can claim to define that culture and ethos. And in the case of the IOC they have very clearly indicated (actually for the past 16 years) that trans women are women, and therefore how can a transwoman competing in a women's sport be considered to be breaking the culture and ethos of a sport which has indicated that they are women. So the argument runs as follows:
1. IOC defines that women's sporting events are for women (a point of principle and I don't think there is any disagreement).
2. The IOC has ruled on a point of principle that transwomen are women and therefore able to compete in women's sports provided they meet specific criteria for eligibility. (I understand that you and others disagree with this, but this is their current principle which is established in their culture and ethos)
3. The IOC sets specific criteria that apply to all potentially eligible competitors (i.e. women - see 2 above) to determine whether they are eligible, largely around testosterone levels.
To have cheated Hubbard would have to have broken some rule or point of principle as set out above - she didn't, she didn't cheat.
What you are effectively saying is that is should be you, or others with a similar view, that should set the ethos of a sport rather than the governing body of that sport. I don't think that is reasonable, although you are quite within your rights to lobby and campaign for the governing body to change any one of 1-3 above. But you should take this up with the governing body rather than label a person, who has complied with all the rule and the broader culture/ethos set out by the governing body, a cheat.