If you have one of those small hand planes, those chrome Stanley planes that are about two and a half inches long, you can make a very exacting cut removing that small part of the lower tongue. Adjust the plane to barely remove a paper thin amount from that tongue.
All you need to do is play with a couple of scraps until you're able to remove exactly the amount you need and no more.
Lay the two pieces on the floor, side by side as if you were going to lift and lock them together.
Take your plane and make one even pass across that lower raised portion of the tongue. Now with both pieces flat on the floor, try and slide them together.
If that doesn't work, make a second pass with the hand plane. Try sliding them together again. At this point put a tapping block on the back side of the piece you're trimming and give it a very gentle tap. If it clicks together, you've probably removed the right amount.
If the piece will tap together, you will still need some additional help with glue, but you haven't totally removed the locking mechanism.
With that said, getting the piece into place can be a little bit of pain depending on how wide it is and how high you cut your door jamb. You may need to remove the plank that this one clicks into, then install the this doorway piece and slide it clear to the wall. Now install the next to the last piece and click it in a place before gluing and tapping in your doorway piece.
Many years ago, I had the same situation with an Armstrong click together floor. For situations like this they requested that you remove .016" off that lower tongue. They say this full well that one out of 10,000 flooring installers has a micrometer or a pair of dial calipers.
......well, that guy is me.
I adjusted my little hand plane and gave it one pass as a trial.
First pass, .016" ..........
.... Just don't ask me to do something like that two times in a row.
The glue can act as a little bit of a lubricant also so that's why you don't need to remove all of that lower tongue. You can actually leave it somewhat tight and it will still tap together with both pieces laying flat. This just takes a little trial and error.
Instead of a hand plan, I'm sure a sanding block would achieve the same result. You do the same as the hand plane. Swipe across the locking mechanism two or three times and test how easy it is to click together. Take note as a number of passes with the sanding block on your test piece and apply that to the locking mechanism on the one that goes into the doorway.