I think there has been a misunderstanding. The phrase "is okay" does not mean "always and only ever use this". Neither is the word "probably" a universal absolute. The text underneath the "is okay" explains that people intuitively view this as a taboo, but it is permissible. I think the reason for the taboo comes from the combination of other patterns such as DDD, ES, and of course EC. But even there it is still permissible to query certain kinds of information from the command side.
Your objection primarily seems to be the specific case of Querying eventually consistent data from the Command side. And in fact, this is still a perfectly valid way (among other possibilities) to get information. I will give you our use cases for example. Configuration data (to control a process) and set validation (unique keys) are our only queries from the command side (each use case also reads from an event stream). For our case, it makes no difference if the configuration data is eventually consistent. When the user makes a configuration change, they are expecting that some processes were executing before they made the change, and some will be executed after. They probably won't notice or care if milliseconds of eventual consistency allowed someone to start a process with the old configuration. Set validation (unique key constraint) is ideally fully consistent, but for us the risk of violation is low enough (they are user-entered with front-end checks and API-side checks) that we are okay with spending admin time to fix it if it ever happens. In our situation it is fine to use these queries with EC. Use your best judgement for your situation.
Thanks for your comments.
I think there has been a misunderstanding. The phrase "is okay" does not mean "always and only ever use this". Neither is the word "probably" a universal absolute. The text underneath the "is okay" explains that people intuitively view this as a taboo, but it is permissible. I think the reason for the taboo comes from the combination of other patterns such as DDD, ES, and of course EC. But even there it is still permissible to query certain kinds of information from the command side.
Your objection primarily seems to be the specific case of Querying eventually consistent data from the Command side. And in fact, this is still a perfectly valid way (among other possibilities) to get information. I will give you our use cases for example. Configuration data (to control a process) and set validation (unique keys) are our only queries from the command side (each use case also reads from an event stream). For our case, it makes no difference if the configuration data is eventually consistent. When the user makes a configuration change, they are expecting that some processes were executing before they made the change, and some will be executed after. They probably won't notice or care if milliseconds of eventual consistency allowed someone to start a process with the old configuration. Set validation (unique key constraint) is ideally fully consistent, but for us the risk of violation is low enough (they are user-entered with front-end checks and API-side checks) that we are okay with spending admin time to fix it if it ever happens. In our situation it is fine to use these queries with EC. Use your best judgement for your situation.
Here is Greg Young's 8-years-old post on the subject.