It only now occurs to me that this is another part of P1’s advantage (or at least his counter to P2’s clear economic advantage, which gets bigger the longer the game goes on). Because whatever P1 plays on T1 will be out of his deck on the first reshuffle - unless P2 has either haste or removal spells/abilities (which are hard to play on T1 anyway).
Whereas P2 might have whateverhe plays on T1 removed “naturally” by P1 on his T2. So P1 has in general a better chance of drawing their T2 techs on T3.
To return to the topic in the OP, I can think of two other interesting aspects of this question. One is that, while you would think of it as a big advantage to draw both of your initial techs on T3 - and very often it is - it can happen that you can’t afford to play both (while also doing other things you may need to do). How much should this impact your decision on what to tech on T2 (should you avoid teching 2 Argonauts/Centaurs because they’re expensive and you don’w want them in the same hand?).
The other one that particularly interest me is that sometimes you have more important things to do on T2 than build Tech 1 - but still usually want to tech at least one Tech 1 unit. If you tech a unit and a spell in this situation, and draw that unit on T3 when you can’t play it, it can kind of hose you (particularly if that unit is important). It will do so even more if you tech 2 units and draw them both, but that’s of course rarer. So it would appear safer in this situation to tech 2 units - but what are the odds?