Are Charged TMs Truly Random?

yep random.
took 2 tms to get wild charge for me

I've done 5 machamps now (my high IV ones all came with counter or heavy slam) sometimes it takes one some times it takes 4 just the way it is.

RNG is totally random. I used 1 charge TM to get Wild Charge. But at the same time, I only got 1 Raikou out of 8 so far. So I am not that mad.

I think it's random. I don't think Niantic is designating one charged move as "best" and making it harder to get, especially as they can go and change the power of any move, number of bars, etc at a whim to make it more or less effective.

After wasting seven early on trying to get Dynamic Punch and STILL not getting it, I have revised my use: no Charged TM unless the result is guaranteed to be unequivocally better than the existing move. And since their rarity has greatly increased, I'm happy with that choice. No more chances at incremental upgrades. Good enough, in many cases, is now indeed good enough.

Your odds of NOT getting what you want:
1 TM = 1/2 (50%)
2 TMs = 1/4 (25%)
3 TMs = 1/8 (12.5%)
4 TMs = 1/16 (6.25%)
5 TMs = 1/32 (3.125%)
6 TMs = 1/64 (1.5625%)

Keep going: sometimes you just roll bad luck.

If you want to think of it this way, your chance of wasting 6 TMs and not getting what you want as a Move is better than your odds of getting a perfect raid pokemon 1/216 . Or a perfectly raid bad 10/10/10 pokemon.