Straggler:
"that it is undesirable to believe a proposition when there is no ground whatever for supposing it true". - Bertrand Russell, Introduction to Sceptical Essays
1) Is this an accurate reflection of scepticism?
2) Is it the approach taken by science?
3) Is it paradoxical and subversive?
Now after having brought you up to this point, in regard to what constitutes "grounds,"...
... I answer your OP again.
Russell ignored the necessity incumbent upon himself, to agree to some axiomatic discipline wherein his scepticism could be put to the test of a Proof.
Hence,
1) No, it is not.
2) No, it is not.
3) Yes, it is paradoxical that Russell would suggest he is sceptical while ignoring the reason we have developed disciplines exactly for the purpose of showing people like him how reasoning can establish truth.
An yes, it is subversive to humanity to support the contention that everything can be doubted at a personal and subjective level simply because one refuses to ground his thinking in one or another of the disciplines of Knowledge.
That is to subvert the very premise that we can think our way through life.