The Obstruction of Congress has no weight, subpoenas weren’t issued under a trial or proceeding, they were illegitimate. That’s one reason why they didn’t have to comply with them, and why Trump could advise them not to go as well. If they were actually subpoenaed during a trial or ACTUAL proceeding which they weren’t then the issues would be different but still could be challenged in court before having to answer them or with EP. The Dems weren’t going to legitimately issue subpoenas because they didn’t want to go through the courts, and didn’t want to fight EP rules, they wouldn’t stand a chance and knew it.