Why does Console and Coin show the 'dirty price' of the Government bond as the buy-average instead of the Clean price?
Console and Coin show the dirty price as the buy average, because that is your actual cost of acquisition.
A non-competitive bidder, will pay the weighted average price (clean price) which emerges in the auction and in addition, also pay interest accrued from the last interest payment date to the date of re-issue of the security. (Accrued interest is calculated using coupon rate and time from last coupon payment).
This is because, on the Interest payment date, you will get paid the interest amount for the entire duration from the previous interest payment date. However, you would've purchased the bond in between and not owned the bond for the entire duration.This is similar to the price adjustments in stock when dividends are issued.
Another reason is that, trading in G-secs on NSE will commence on December 17, 2018 and trading in G-SEC shall be inclusive of accrued interest i.e. dirty price.