It's been known for a long time that Summoning Portal has a priority earlier than most cost modifiers. If you play a Mechwarper then a Portal, a 2-cost Mech still goes down to 0. This was presumed to be intended for a while.
Reckless Experimenter, however, does not have the same early priority following the addition of a similar clause in its text. Currently, it has a late one, but one of the devs has mentioned that they're looking to move it to an even priority. They describe how this would make Mechwarper+Experimenter affected by order of play:
https://www.reddit.com/r/hearthstone/comments/bwfy7c/reckless_experimenter_does_not_work_in/epxnkrl/
Both the current behavior and described intended behavior for Experimenter is inconsistent with the current behavior for Portal. So either:
Summoning Portal is not working as intended.
Summoning Portal is working as intended and the discrepancy is related to the minor wording difference.
Summoning Portal is working as intended but the inconsistency is an oversight.
Fixed an issue where Summoning Portal and Reckless Experimenter's effects were being applied at different timings than other similar cost modification effects.
It's been known for a long time that Summoning Portal has a priority earlier than most cost modifiers. If you play a Mechwarper then a Portal, a 2-cost Mech still goes down to 0. This was presumed to be intended for a while.
Reckless Experimenter, however, does not have the same early priority following the addition of a similar clause in its text. Currently, it has a late one, but one of the devs has mentioned that they're looking to move it to an even priority. They describe how this would make Mechwarper+Experimenter affected by order of play: https://www.reddit.com/r/hearthstone/comments/bwfy7c/reckless_experimenter_does_not_work_in/epxnkrl/
Both the current behavior and described intended behavior for Experimenter is inconsistent with the current behavior for Portal. So either: