is their some kind of musical force that explains how slow tempos envelope fast tempos when listening to their sonic clash?

No, there is no musical theory which states this.

Is McLaughlin suggesting that the musicians from the first part will naturally adjust their playing to meet with the orchestra's playing?

No, what he means is that, by crescendoing dynamically from the background to the foreground, the slower tempo will take over the listener's attention. It's due to the dynamic and textural changes that the slower tempo becomes dominant.

Can someone explain this harmony/entropy of tempo?

I will be extremely brief, but tempos can be thought of as dissonant vs. consonant to one-another based upon the common denominator. For example 120 and 240 are "consonant" because one in twice the speed of the other. 60 and 90 are a bit more dissonant, but still related by a 3/2-multiple.

In your example 138 and 304 are entirely dissonant because there is no multiplier that can relate them to one another. One would have to wait a very long time for barlines in the two tempos to coincide.

These tempos would seem to have been chosen specifically by the composer for this dissonant effect of non-correlated tempos

is their some kind of musical force that explains how slow tempos envelope fast tempos when listening to their sonic clash?

No, there is no musical theory which states this.

Is McLaughlin suggesting that the musicians from the first part will naturally adjust their playing to meet with the orchestra's playing?

No, what he means is that, by crescendoing dynamically from the background to the foreground, the slower tempo will take over the listener's attention. It's due to the dynamic and textural changes that the slower tempo becomes dominant.

Can someone explain this harmony/entropy of tempo?

I will be extremely brief, but tempos can be thought of as dissonant vs. consonant to one-another based upon the common denominator. For example 120 and 240 are "consonant" because one is twice the speed of the other. 60 and 90 are a bit more dissonant, but still related by a 3/2-multiple (i.e. you will still have regular coinciding beats and barlines).

In your example 138 and 304 are entirely dissonant because there is no multiplier that can relate them to one another. One would have to wait a very long time for barlines in the two tempos to coincide.

These tempos would seem to have been chosen specifically by the composer for this dissonant effect of non-correlated tempos