What is the thing at 1:19?
It's basically what you see. Tanimoto sensei says that even though he's taking ukemi here "his heart is still standing"..which allows him to do this....i.e he doesn't lay down and "give up" but maintains awareness and connection at all times. Of course in every dojo/organisation there are people of different strengths/sensitivity, and every uke is different too...so what feels cold for some feels hot for others. This is a simple explanation btw...
I should say that there is a great sense of joy in his practise and this is reflected in everyone who trains with him. Practise is quite simply a pleasure and good fun too. It's very important to maintain the correct feeling towards your partner..he happily says he always feels love for anyone he practises with.
Some can go very wrong with feeling things like I must show great strength/power...trying to show people the mat ^^....that will actually hinder development in true aikido in many ways imho.
Some other shihan often try to say the same things but in different ways...and for sure if you can't do things well slowly, you can't do them well fast : )
All the best