Thanks for the chapter!
Looks like Miyabi has a big crush on MC and really feeling the contact with him. As for comment about teleporting aparently it's a high tier level spell but being a muscle brain she isn't able to memorize and understand it well enough to use it. Like being given a high level mathematical formula for solving a problem in quantum physics but only able to understand basic math. Seems she doesn't fully understand the implications or own reactions to teasing MC along with him actually carrying out what she says.
LN describes it better but reason behind the training with Miyabi is to improve his physical stats. Seems to have been edited out here but in LN reason she gives is that the stronger his physical base is, the stronger the magical buff that increases his physical stats. Also, that having a supreme spell won't help him if he's bedridden and can't move. Basically in buffing if spell doubles his strength, for example, if his base stat is 1 then it only gets buffed to 2 while a base of 5 would increase to 10. That, and having great magic won't help him if his body gives out, or runs out of energy or stamina resulting in him being unable to cast the magic. For example, if shooting an enemy with a rocket launcher you can't take them out if can't lift and aim the launcher to hit them. Not to mention if need more than one shot but can't reload fast enough or unable to provide/carry enough material for additional shots. Like either couldn't carry even one extra rocket to shoot or took so long to reload launcher enemy had already had more than enough time to take him out leisurely.